Fix swagger correctness for appplatform 2021-06-01-preview (#15031)

Author: gavinfish

specification/appplatform/resource-manager/Microsoft.AppPlatform/preview/2021-06-01-preview/appplatform.json

@@ -3066,23 +3066,43 @@
       "properties": {
         "serviceRuntimeSubnetId": {
           "description": "Fully qualified resource Id of the subnet to host Azure Spring Cloud Service Runtime",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "appSubnetId": {
           "description": "Fully qualified resource Id of the subnet to host Azure Spring Cloud Apps",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "serviceCidr": {
           "description": "Azure Spring Cloud service reserved CIDR",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "serviceRuntimeNetworkResourceGroup": {
           "description": "Name of the resource group containing network resources of Azure Spring Cloud Service Runtime",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "appNetworkResourceGroup": {
           "description": "Name of the resource group containing network resources of Azure Spring Cloud Apps",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "outboundIPs": {
           "description": "Desired outbound IP resources for Azure Spring Cloud instance.",
@@ -3413,11 +3433,16 @@
         },
         "fqdn": {
           "description": "Fully qualified dns Name.",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "httpsOnly": {
           "description": "Indicate if only https is allowed.",
-          "type": "boolean"
+          "type": "boolean",
+          "default": false
         },
         "createdTime": {
           "format": "date-time",
@@ -3435,7 +3460,8 @@
         },
         "enableEndToEndTLS": {
           "description": "Indicate if end to end TLS is enabled.",
-          "type": "boolean"
+          "type": "boolean",
+          "default": false
         }
       }
     },
@@ -3452,7 +3478,8 @@
         },
         "mountPath": {
           "description": "Mount path of the temporary disk",
-          "type": "string"
+          "type": "string",
+          "default": "/tmp"
         }
       }
     },
@@ -4018,6 +4045,7 @@
         },
         "runtimeVersion": {
           "description": "Runtime version",
+          "default": "Java_8",
           "enum": [
             "Java_8",
             "Java_11",