introduce the modelfactory for resourcemanager (Azure#32749)

* introduce the modelfactory

* fix namespace

Author: ArcturusZhang

sdk/resourcemanager/Azure.ResourceManager/api/Azure.ResourceManager.netstandard2.0.cs

@@ -449,6 +449,11 @@ protected ResourceData(Azure.Core.ResourceIdentifier id, string name, Azure.Core
         public Azure.Core.ResourceType ResourceType { get { throw null; } }
         public Azure.ResourceManager.Models.SystemData SystemData { get { throw null; } }
     }
+    public static partial class ResourceManagerModelFactory
+    {
+        public static Azure.ResourceManager.Resources.Models.SubResource SubResource(Azure.Core.ResourceIdentifier id = null) { throw null; }
+        public static Azure.ResourceManager.Resources.Models.WritableSubResource WritableSubResource(Azure.Core.ResourceIdentifier id = null) { throw null; }
+    }
     [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
     [System.ObsoleteAttribute("This type is obsolete and will be removed in a future release.", false)]
     public partial class SystemAssignedServiceIdentity

sdk/resourcemanager/Azure.ResourceManager/src/Resources/Custom/ResourceManagerModelFactory.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using Azure.Core;
+using Azure.ResourceManager.Resources.Models;
+
+namespace Azure.ResourceManager.Models
+{
+    /// <summary> Model factory for read-only models. </summary>
+    public static partial class ResourceManagerModelFactory
+    {
+        /// <summary> Initializes a new instance of SubResource. </summary>
+        /// <param name="id"></param>
+        /// <returns> A new <see cref="Resources.Models.SubResource"/> instance for mocking. </returns>
+        public static SubResource SubResource(ResourceIdentifier id = null)
+        {
+            return new SubResource(id);
+        }
+
+        /// <summary> Initializes a new instance of WritableSubResource. </summary>
+        /// <param name="id"></param>
+        /// <returns> A new <see cref="Resources.Models.WritableSubResource"/> instance for mocking. </returns>
+        public static WritableSubResource WritableSubResource(ResourceIdentifier id = null)
+        {
+            return new WritableSubResource(id);
+        }
+    }
+}