Add AML skill to preview swagger for Search Service (#16910)

* add aml skill to preview swagger for search service'

* update

specification/search/data-plane/Azure.Search/preview/2021-04-30-Preview/searchservice.json

@@ -8571,6 +8571,52 @@
       },
       "description": "A dictionary of http request headers."
     },
+    "AmlSkill": {
+      "x-ms-discriminator-value": "#Microsoft.Skills.Custom.AmlSkill",
+      "allOf": [
+        {
+          "$ref": "#/definitions/SearchIndexerSkill"
+        }
+      ],
+      "properties": {
+        "uri": {
+          "type": "string",
+          "x-nullable": true,
+          "description": "(Required for no authentication or key authentication) The scoring URI of the AML service to which the JSON payload will be sent. Only the https URI scheme is allowed."
+        },
+        "key": {
+          "type": "string",
+          "x-nullable": true,
+          "description": "(Required for key authentication) The key for the AML service."
+        },
+        "resourceId": {
+          "type": "string",
+          "x-nullable": true,
+          "description": "(Required for token authentication). The Azure Resource Manager resource ID of the AML service. It should be in the format subscriptions/{guid}/resourceGroups/{resource-group-name}/Microsoft.MachineLearningServices/workspaces/{workspace-name}/services/{service_name}."
+        },
+        "timeout": {
+          "type": "string",
+          "format": "duration",
+          "x-nullable": true,
+          "description": "(Optional) When specified, indicates the timeout for the http client making the API call."
+        },
+        "region": {
+          "type": "string",
+          "x-nullable": true,
+          "description": "(Optional for token authentication). The region the AML service is deployed in."
+        },
+        "degreeOfParallelism": {
+          "type": "integer",
+          "format": "int32",
+          "x-nullable": true,
+          "description": "(Optional) When specified, indicates the number of calls the indexer will make in parallel to the endpoint you have provided. You can decrease this value if your endpoint is failing under too high of a request load, or raise it if your endpoint is able to accept more requests and you would like an increase in the performance of the indexer. If not set, a default value of 5 is used. The degreeOfParallelism can be set to a maximum of 10 and a minimum of 1."
+        }
+      },
+      "externalDocs": {
+        "url": "https://docs.microsoft.com/en-us/azure/search/cognitive-search-aml-skill"
+      },
+      "description": "The AML skill allows you to extend AI enrichment with a custom Azure Machine Learning (AML) model. Once an AML model is trained and deployed, an AML skill integrates it into AI enrichment."
+    },
     "ListSkillsetsResult": {
       "properties": {
         "value": {