[WebPubSub] Init the Microsoft.Azure.WebPubSub.Common proj. (Azure#24359)

# All SDK Contribution checklist:

This checklist is used to make sure that common guidelines for a pull request are followed.
- [ ] **Please open PR in `Draft` mode if it is:**
	- Work in progress or not intended to be merged.
	- Encountering multiple pipeline failures and working on fixes.
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- [ ] **I have read the [contribution guidelines](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md).**
- [ ] **The pull request does not introduce [breaking changes](https://github.com/dotnet/corefx/blob/master/Documentation/coding-guidelines/breaking-change-rules.md).**

### [General Guidelines and Best Practices](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md#general-guidelines)
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- [ ] Pull request includes test coverage for the included changes.

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- [ ] The generate.cmd file for the SDK has been updated with the version of AutoRest, as well as the commitid of your swagger spec or link to the swagger spec, used to generate the code. (Track 2 only)
- [ ] The `*.csproj` and `AssemblyInfo.cs` files have been updated with the new version of the SDK. Please double check nuget.org current release version.

## Additional management plane SDK specific contribution checklist: 
Note: Only applies to `Microsoft.Azure.Management.[RP]` or `Azure.ResourceManager.[RP]`
 
- [ ] Include updated [management metadata](https://github.com/Azure/azure-sdk-for-net/tree/main/eng/mgmt/mgmtmetadata).
- [ ] Update AzureRP.props to add/remove version info to maintain up to date API versions.

### Management plane SDK Troubleshooting
- If this is very first SDK for a services and you are adding new service folders directly under /SDK, please add `new service` label and/or contact assigned reviewer.
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	- Do not modify any code in generated folders.
	- Do not selectively include/remove generated files in the PR.
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	Please pay attention to the @microsoft.csharp version output after running `generate.ps1`. If it is lower than current released version (2.3.82), please run it again as it should pull down the latest version.
	
	**Note: We have recently updated the PSH module called by `generate.ps1` to emit additional data. This would help reduce/eliminate the Code Verification check error. Please run following command**:

	    `dotnet msbuild eng/mgmt.proj /t:Util /p:UtilityName=InstallPsModules`

### Old outstanding PR cleanup
 Please note:
	If PRs (including draft) has been out for more than 60 days and there are no responses from our query or followups, they will be closed to maintain a concise list for our reviewers.

Author: JialinXin

eng/Packages.Data.props

@@ -37,6 +37,7 @@
     <PackageReference Update="System.Globalization" Version="4.3.0" />
     <PackageReference Update="System.IdentityModel.Tokens.Jwt" Version="5.4.0" />
     <PackageReference Update="System.Linq" Version="4.3.0" />
+    <PackageReference Update="System.Memory.Data" Version="1.0.2" />
     <PackageReference Update="System.Net.Http" Version="4.3.4" />
     <PackageReference Update="System.Reflection.TypeExtensions" Version="[4.5.1, 4.9.0)" />
     <PackageReference Update="System.Runtime.Extensions" Version="4.3.0" />
@@ -46,6 +47,7 @@
     <PackageReference Update="System.Security.Cryptography.Cng" Version="4.3.0" />
     <PackageReference Update="System.Security.Cryptography.Primitives" Version="4.3.0" />
     <PackageReference Update="System.Text.Encodings.Web" Version="4.5.1" />
+    <PackageReference Update="System.Text.Json" Version="4.6.0" />
     <PackageReference Update="System.ValueTuple" Version="4.5.0" />
 
     <PackageReference Update="WindowsAzure.Storage" Version="9.3.3" />

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/CHANGELOG.md

@@ -0,0 +1,7 @@
+# Release History
+
+## 1.0.0-beta.1 (Unreleased)
+
+### Features Added
+
+- Common library to define the upstream requests and responses from Service to Server in Azure Web PubSub service.

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/Directory.Build.props

@@ -0,0 +1,6 @@
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <!--
+    Add any shared properties you want for the projects under this package directory that need to be set before the auto imported Directory.Build.props
+  -->
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory).., Directory.Build.props))\Directory.Build.props" />
+</Project>

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/README.md

@@ -0,0 +1,65 @@
+# Azure Web PubSub Event Handler events data model client library for .NET
+
+This library defines the class to process with Azure Web PubSub service upstream requests.
+
+## Getting started
+
+### Install the package
+
+Install the client library from [NuGet](https://www.nuget.org/):
+
+```dotnetcli
+dotnet add package Microsoft.Azure.WebPubSub.Common
+```
+
+### Prerequisites
+
+- An [Azure subscription][azure_sub].
+- An existing Azure Web PubSub service instance.
+
+### Authenticate the client
+
+Not applicable for the library. You should work with a client library to deserialize service requests in a friendly way.
+
+## Key concepts
+
+### Events
+
+Connect, Connected, Disconnected are system events indicate connection stage. And Connect is a blocking event that service will wait for the response to determine next action. Any error returned will drop the connection.
+
+User events are message event. It's also a blocking event which service is waiting for response. And server can return information in the response which will be sent to the caller directly.
+
+### WebPubSubEventRequest
+
+WebPubSubEventRequest, represents a abstract request come from service side. In detail, it should be ValidationRequest or one of the 4 events, which are ConnectEventRequest, ConnectedEventRequest, UserEventRequest and DisconnectedEventRequest. ValidationRequest represent the request for [Abuse Protection](https://github.com/cloudevents/spec/blob/v1.0.1/http-webhook.md#4-abuse-protection).
+
+### WebPubSubEventResponse
+
+WebPubSubEventResponse, represents a abstract response should return to service. In detail, it should be EventErrorResponse or one of the 2 blocking events, which are ConnectEventResponse and UserEventResponse.
+
+## Examples
+
+Check Microsoft.Azure.WebPubSub.AspNetCore for E2E using examples.
+
+## Troubleshooting
+
+You can also easily [enable console logging](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/core/Azure.Core/samples/Diagnostics.md#logging) if you want to dig deeper into the requests you're making against the service.
+
+## Next steps
+
+Please take a look at the
+[samples][samples_ref]
+directory for detailed examples on how to use this library.
+
+## Contributing
+
+This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit <https://cla.microsoft.com>.
+
+When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.
+
+This project has adopted the [Microsoft Open Source Code of Conduct][code_of_conduct]. For more information see the [Code of Conduct FAQ][code_of_conduct_faq] or contact opencode@microsoft.com with any additional questions or comments.
+
+![Impressions](https://azure-sdk-impressions.azurewebsites.net/api/impressions/azure-sdk-for-net%2Fsdk%2Feventgrid%2FMicrosoft.Azure.Messaging.EventGrid.CloudNativeCloudEvents%2FREADME.png)
+
+[azure_sub]: https://azure.microsoft.com/free/dotnet/
+[samples_ref]: https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/webpubsub/Azure.Messaging.WebPubSub/tests/Samples/

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/Internal/BinaryDataJsonConverter.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace System
+{
+    internal class BinaryDataJsonConverter : JsonConverter<BinaryData>
+    {
+        public override BinaryData Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            if (reader.TokenType == JsonTokenType.String)
+            {
+                return BinaryData.FromString(JsonSerializer.Deserialize<string>(ref reader));
+            }
+
+            if (TryLoadBinary(ref reader, out var bytes))
+            {
+                return BinaryData.FromBytes(bytes);
+            }
+
+            // string object
+            return BinaryData.FromString(reader.GetString());
+        }
+
+        public override void Write(Utf8JsonWriter writer, BinaryData value, JsonSerializerOptions options)
+        {
+            writer.WriteStringValue(value.ToString());
+        }
+
+        private static bool TryLoadBinary(ref Utf8JsonReader input, out byte[] output)
+        {
+            var doc = JsonDocument.ParseValue(ref input);
+            if (doc.RootElement.TryGetProperty("type", out var value) && value.GetString().Equals("Buffer", StringComparison.OrdinalIgnoreCase)
+                && doc.RootElement.TryGetProperty("data", out var data))
+            {
+                output = JsonSerializer.Deserialize<List<byte>>(data.GetRawText()).ToArray();
+                return true;
+            }
+            output = null;
+            return false;
+        }
+    }
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/Internal/ConnectEventRequestJsonConverter.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Azure.WebPubSub.Common
+{
+    internal class ConnectEventRequestJsonConverter : JsonConverter<ConnectEventRequest>
+    {
+        public override ConnectEventRequest Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var element = JsonDocument.ParseValue(ref reader).RootElement;
+
+            return new ConnectEventRequest(
+                element.ReadToObject<Dictionary<string, string[]>>(ConnectEventRequest.ClaimsProperty),
+                element.ReadToObject<Dictionary<string, string[]>>(ConnectEventRequest.QueryProperty),
+                element.ReadToObject<string[]>(ConnectEventRequest.SubprotocolsProperty),
+                element.ReadToObject<WebPubSubClientCertificate[]>(ConnectEventRequest.ClientCertificatesProperty));
+        }
+
+        public override void Write(Utf8JsonWriter writer, ConnectEventRequest value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+            writer.WritePropertyName(ConnectEventRequest.ClaimsProperty);
+            JsonSerializer.Serialize(writer, value.Claims, options);
+            writer.WritePropertyName(ConnectEventRequest.QueryProperty);
+            JsonSerializer.Serialize(writer, value.Query, options);
+            writer.WritePropertyName(ConnectEventRequest.SubprotocolsProperty);
+            JsonSerializer.Serialize(writer, value.Subprotocols, options);
+            writer.WritePropertyName(ConnectEventRequest.ClientCertificatesProperty);
+            JsonSerializer.Serialize(writer, value.ClientCertificates, options);
+            if (value.ConnectionContext != null)
+            {
+                writer.WritePropertyName(WebPubSubEventRequest.ConnectionContextProperty);
+                JsonSerializer.Serialize(writer, value.ConnectionContext, options);
+            }
+            writer.WriteEndObject();
+        }
+    }
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/Internal/DisconnectedEventRequestJsonConverter.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Azure.WebPubSub.Common
+{
+    internal class DisconnectedEventRequestJsonConverter : JsonConverter<DisconnectedEventRequest>
+    {
+        public override DisconnectedEventRequest Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var element = JsonDocument.ParseValue(ref reader).RootElement;
+
+            return new DisconnectedEventRequest(element.ReadString(DisconnectedEventRequest.ReasonProperty));
+        }
+
+        public override void Write(Utf8JsonWriter writer, DisconnectedEventRequest value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+            writer.WritePropertyName(DisconnectedEventRequest.ReasonProperty);
+            JsonSerializer.Serialize(writer, value.Reason, options);
+            if (value.ConnectionContext != null)
+            {
+                writer.WritePropertyName(WebPubSubEventRequest.ConnectionContextProperty);
+                JsonSerializer.Serialize(writer, value.ConnectionContext, options);
+            }
+            writer.WriteEndObject();
+        }
+    }
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/Internal/JsonElementExtensions.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+namespace System.Text.Json
+{
+    internal static class JsonElementExtensions
+    {
+        public static string ReadString(this JsonElement element, string name)
+        {
+            return element.GetProperty(name).GetString();
+        }
+
+        public static TValue ReadToObject<TValue>(this JsonElement element, string name)
+        {
+            var value = element.GetProperty(name);
+            return JsonSerializer.Deserialize<TValue>(value.GetRawText());
+        }
+    }
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/Internal/WebPubSubClientCertificateJsonConverter.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Azure.WebPubSub.Common
+{
+    internal class WebPubSubClientCertificateJsonConverter : JsonConverter<WebPubSubClientCertificate>
+    {
+        public override WebPubSubClientCertificate Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var element = JsonDocument.ParseValue(ref reader).RootElement;
+
+            return new WebPubSubClientCertificate(
+                element.ReadString(WebPubSubClientCertificate.ThumbprintProperty));
+        }
+
+        public override void Write(Utf8JsonWriter writer, WebPubSubClientCertificate value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+            writer.WritePropertyName(WebPubSubClientCertificate.ThumbprintProperty);
+            JsonSerializer.Serialize(writer, value.Thumbprint, options);
+            writer.WriteEndObject();
+        }
+    }
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.Common/src/MessageDataType.cs

@@ -0,0 +1,24 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.WebPubSub.Common
+{
+    /// <summary>
+    /// Message data type.
+    /// </summary>
+    public enum MessageDataType
+    {
+        /// <summary>
+        /// binary of content type application/octet-stream.
+        /// </summary>
+        Binary,
+        /// <summary>
+        /// json of content type application/json.
+        /// </summary>
+        Json,
+        /// <summary>
+        /// text of content type text/plain.
+        /// </summary>
+        Text
+    }
+}