Add UserNameSecurityToken to public api's

Author: mconnew

src/System.ServiceModel.Http/src/System/ServiceModel/Channels/HttpChannelFactory.cs

@@ -1038,6 +1038,7 @@ public async Task SendRequestAsync(Message message, TimeoutHelper timeoutHelper)
                             {
                                 // For MTOM messages, add a MIME version header
                                 AddMimeVersion("1.0");
+                                request.Properties.Add("System.ServiceModel.Channel.MtomMessageEncoder.WriteMessageHeaders", false);
                             }
 
                         }

src/System.ServiceModel.Primitives/ref/System.ServiceModel.Security.cs

@@ -475,6 +475,17 @@ public SecurityTokenValidationException(string message) { }
         public SecurityTokenValidationException(string message, System.Exception innerException)  { }
         protected SecurityTokenValidationException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) { }
     }
+    public partial class UserNameSecurityToken : SecurityToken
+    {
+        public UserNameSecurityToken(string userName, string password) { }
+        public UserNameSecurityToken(string userName, string password, string id) { }
+        public override string Id => default;
+        public override System.Collections.ObjectModel.ReadOnlyCollection<SecurityKey> SecurityKeys => default;
+        public override DateTime ValidFrom => default;
+        public override DateTime ValidTo => default;
+        public string UserName => default;
+        public string Password => default;
+    }
     public partial class X509SecurityToken : SecurityToken, IDisposable
     {
         public X509SecurityToken(System.Security.Cryptography.X509Certificates.X509Certificate2 certificate) { }

src/System.ServiceModel.Primitives/src/System/ServiceModel/Channels/MtomMessageEncoder.cs

@@ -423,12 +423,12 @@ public override Message ReadMessage(Stream stream, int maxSizeOfHeaders, string
 
         public override ArraySegment<byte> WriteMessage(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
         {
-            return WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false);
+            return WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri);
         }
 
         public override ValueTask<ArraySegment<byte>> WriteMessageAsync(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
         {
-            return new ValueTask<ArraySegment<byte>>(WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false));
+            return new ValueTask<ArraySegment<byte>>(WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri));
         }
 
         private string GetContentType(out string boundary)
@@ -446,8 +446,14 @@ internal string FormatContentType(string boundary, string startInfo)
                 MtomContentType, MtomStartUri, boundary, startInfo);
         }
 
-        private ArraySegment<byte> WriteMessageInternal(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset, string startInfo, string boundary, string startUri, bool writeMessageHeaders)
+        private ArraySegment<byte> WriteMessageInternal(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset, string startInfo, string boundary, string startUri)
         {
+            bool writeMessageHeaders = true;
+            if (message.Properties.TryGetValue("System.ServiceModel.Channel.MtomMessageEncoder.WriteMessageHeaders", out object boolAsObject) && boolAsObject is bool)
+            {
+                writeMessageHeaders = (bool)boolAsObject;
+            }
+
             if (message == null)
                 throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull(nameof(message));
             if (bufferManager == null)
@@ -517,7 +523,7 @@ public override void WriteMessage(Message message, Stream stream)
 
         public override ValueTask WriteMessageAsync(Message message, Stream stream)
         {
-            return WriteMessageInternalAsync(message, stream, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false);
+            return WriteMessageInternalAsync(message, stream, GenerateStartInfoString(), _boundary, MtomStartUri);
         }
 
         public override IAsyncResult BeginWriteMessage(Message message, Stream stream, AsyncCallback callback, object state)
@@ -530,8 +536,14 @@ public override void EndWriteMessage(IAsyncResult result)
             result.ToApmEnd();
         }
 
-        private async ValueTask WriteMessageInternalAsync(Message message, Stream stream, string startInfo, string boundary, string startUri, bool writeMessageHeaders)
+        private async ValueTask WriteMessageInternalAsync(Message message, Stream stream, string startInfo, string boundary, string startUri)
         {
+            bool writeMessageHeaders = true;
+            if (message.Properties.TryGetValue("System.ServiceModel.Channel.MtomMessageEncoder.WriteMessageHeaders", out object boolAsObject) && boolAsObject is bool)
+            {
+                writeMessageHeaders = (bool)boolAsObject;
+            }
+
             if (message == null)
                 throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentNullException(nameof(message)));
             if (stream == null)