[ReleasePR synapse] Add userAssignedIdentities property to the Identity section in 2021-05-01 and 2021-06-01-preview (#1819)

Create to sync Azure/azure-rest-api-specs#15296
[ReCreate this PR](https://github.com/azure-resource-manager-schemas/compare/master...AzureSDKAutomation:sdkAuto/synapse?expand=1)

Author: msftbot[bot]

schemas/2021-05-01/Microsoft.Synapse.json

@@ -3095,14 +3095,30 @@
               "type": "string",
               "enum": [
                 "None",
-                "SystemAssigned"
+                "SystemAssigned",
+                "SystemAssigned,UserAssigned"
               ]
             },
             {
               "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
             }
           ],
           "description": "The type of managed identity for the workspace."
+        },
+        "userAssignedIdentities": {
+          "oneOf": [
+            {
+              "type": "object",
+              "additionalProperties": {
+                "$ref": "#/definitions/UserAssignedManagedIdentity"
+              },
+              "properties": {}
+            },
+            {
+              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
+            }
+          ],
+          "description": "The User Assigned Managed Identities."
         }
       },
       "description": "The workspace managed identity"
@@ -4045,6 +4061,11 @@
       },
       "description": "Represents the properties of a database transparent data encryption."
     },
+    "UserAssignedManagedIdentity": {
+      "type": "object",
+      "properties": {},
+      "description": "User Assigned Managed Identity"
+    },
     "VirtualNetworkProfile": {
       "type": "object",
       "properties": {

schemas/2021-06-01-preview/Microsoft.Synapse.json

@@ -4120,14 +4120,30 @@
               "type": "string",
               "enum": [
                 "None",
-                "SystemAssigned"
+                "SystemAssigned",
+                "SystemAssigned,UserAssigned"
               ]
             },
             {
               "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
             }
           ],
           "description": "The type of managed identity for the workspace."
+        },
+        "userAssignedIdentities": {
+          "oneOf": [
+            {
+              "type": "object",
+              "additionalProperties": {
+                "$ref": "#/definitions/UserAssignedManagedIdentity"
+              },
+              "properties": {}
+            },
+            {
+              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
+            }
+          ],
+          "description": "The User Assigned Managed Identities."
         }
       },
       "description": "The workspace managed identity"
@@ -5289,6 +5305,11 @@
       },
       "description": "Represents the properties of a database transparent data encryption."
     },
+    "UserAssignedManagedIdentity": {
+      "type": "object",
+      "properties": {},
+      "description": "User Assigned Managed Identity"
+    },
     "VirtualNetworkProfile": {
       "type": "object",
       "properties": {