Add required fields to ClientConnection (Azure#51338)

Author: nick863

sdk/core/System.ClientModel/api/System.ClientModel.net8.0.cs

@@ -129,6 +129,7 @@ public readonly partial struct ClientConnection
         public System.ClientModel.Primitives.CredentialKind CredentialKind { get { throw null; } }
         public string Id { get { throw null; } }
         public string Locator { get { throw null; } }
+        public System.Collections.Generic.IReadOnlyDictionary<string, string> Metadata { get { throw null; } }
         public override string ToString() { throw null; }
         public bool TryGetLocatorAsUri(out System.Uri? uri) { throw null; }
     }

sdk/core/System.ClientModel/api/System.ClientModel.netstandard2.0.cs

@@ -128,6 +128,7 @@ public readonly partial struct ClientConnection
         public System.ClientModel.Primitives.CredentialKind CredentialKind { get { throw null; } }
         public string Id { get { throw null; } }
         public string Locator { get { throw null; } }
+        public System.Collections.Generic.IReadOnlyDictionary<string, string> Metadata { get { throw null; } }
         public override string ToString() { throw null; }
         public bool TryGetLocatorAsUri(out System.Uri? uri) { throw null; }
     }

sdk/core/System.ClientModel/src/Convenience/ClientConnection.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
+using System.Collections.ObjectModel;
 
 namespace System.ClientModel.Primitives;
 
@@ -28,6 +29,7 @@ public ClientConnection(string id, string locator, object credential, Credential
         Locator = locator;
         Credential = credential;
         CredentialKind = credentialKind;
+        Metadata = new Dictionary<string, string>();
     }
 
     /// <summary>
@@ -45,6 +47,7 @@ public ClientConnection(string id, string locator)
         Id = id;
         Locator = locator;
         CredentialKind = CredentialKind.None;
+        Metadata = new ReadOnlyDictionary<string, string>(new Dictionary<string, string>());
     }
 
     /// <summary>
@@ -59,6 +62,23 @@ internal ClientConnection(string id, string locator, CredentialKind credentialKi
         Id = id;
         Locator = locator;
         CredentialKind = credentialKind;
+        Metadata = new ReadOnlyDictionary<string, string>(new Dictionary<string, string>());
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ClientConnection"/> struct with the specified subclient ID.
+    /// It is only for the JSON serializer.
+    /// </summary>
+    /// <param name="metadata">The connection metadata.</param>
+    /// <param name="id">The identifier for the connection.</param>
+    /// <param name="locator">The endpoint or resource identifier.</param>
+    /// <param name="credentialKind">The kind of connection used by the client</param>
+    internal ClientConnection(IReadOnlyDictionary<string, string> metadata, string id, string locator, CredentialKind credentialKind)
+    {
+        Id = id;
+        Locator = locator;
+        CredentialKind = credentialKind;
+        Metadata = metadata;
     }
 
     /// <summary>
@@ -96,4 +116,7 @@ public bool TryGetLocatorAsUri(out Uri? uri)
     /// </summary>
     /// <returns>A string in the format 'Id => Locator'.</returns>
     public override string ToString() => $"{Id} => {Locator}";
+
+    /// <summary> Metadata of the connection. </summary>
+    public IReadOnlyDictionary<string, string> Metadata { get; }
 }