[ReleasePR timeseriesinsights] [Hub Generated] Public private branch 'add-ingressStartAt' (#1762)

Create to sync Azure/azure-rest-api-specs#13932
[ReCreate this PR](https://github.com/azure-resource-manager-schemas/compare/master...AzureSDKAutomation:sdkAuto/timeseriesinsights?expand=1)

Author: msftbot[bot]

schemas/2020-05-15/Microsoft.TimeSeriesInsights.json

@@ -488,6 +488,17 @@
           "type": "string",
           "description": "The resource id of the event source in Azure Resource Manager."
         },
+        "ingressStartAt": {
+          "oneOf": [
+            {
+              "$ref": "#/definitions/IngressStartAtProperties"
+            },
+            {
+              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
+            }
+          ],
+          "description": "An object that contains the details about the starting point in time to ingest events."
+        },
         "keyName": {
           "type": "string",
           "description": "The name of the SAS key that grants the Time Series Insights service access to the event hub. The shared access policies for this key must grant 'Listen' permissions to the event hub."
@@ -695,6 +706,32 @@
       ],
       "description": "The storage configuration provides the connection details that allows the Time Series Insights service to connect to the customer storage account that is used to store the environment's data."
     },
+    "IngressStartAtProperties": {
+      "type": "object",
+      "properties": {
+        "time": {
+          "type": "string",
+          "description": "ISO8601 UTC datetime with seconds precision (milliseconds are optional), specifying the date and time that will be the starting point for Events to be consumed."
+        },
+        "type": {
+          "oneOf": [
+            {
+              "type": "string",
+              "enum": [
+                "EarliestAvailable",
+                "EventSourceCreationTime",
+                "CustomEnqueuedTime"
+              ]
+            },
+            {
+              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
+            }
+          ],
+          "description": "The type of the ingressStartAt, It can be \"EarliestAvailable\", \"EventSourceCreationTime\", \"CustomEnqueuedTime\"."
+        }
+      },
+      "description": "An object that contains the details about the starting point in time to ingest events."
+    },
     "IoTHubEventSourceCreateOrUpdateParameters": {
       "type": "object",
       "properties": {
@@ -733,6 +770,17 @@
           "type": "string",
           "description": "The resource id of the event source in Azure Resource Manager."
         },
+        "ingressStartAt": {
+          "oneOf": [
+            {
+              "$ref": "#/definitions/IngressStartAtProperties"
+            },
+            {
+              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
+            }
+          ],
+          "description": "An object that contains the details about the starting point in time to ingest events."
+        },
         "iotHubName": {
           "type": "string",
           "description": "The name of the iot hub."