Log a warning when hostobject found with no creds (#228)

Author: benvillalobos

Microsoft.NET.Build.Containers/CreateNewImageToolTask.cs

@@ -156,7 +156,7 @@ string responseFileSwitch
     )
     {
         VSHostObject hostObj = new VSHostObject(HostObject as System.Collections.Generic.IEnumerable<ITaskItem>);
-        if (hostObj.ExtractCredentials(out string user, out string pass))
+        if (hostObj.ExtractCredentials(out string user, out string pass, (string s) => Log.LogWarning(s)))
         {
             extractionInfo = (true, user, pass);
         }

Microsoft.NET.Build.Containers/VSHostObject.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.Build.Framework;
@@ -16,7 +17,7 @@ public VSHostObject(IEnumerable<ITaskItem>? hostObject)
         _hostObject = hostObject;
     }
 
-    public bool ExtractCredentials(out string username, out string password)
+    public bool ExtractCredentials(out string username, out string password, Action<string> logMethod)
     {
         bool retVal = false;
         username = password = string.Empty;
@@ -31,6 +32,10 @@ public bool ExtractCredentials(out string username, out string password)
                 {
                     password = credentialItem.GetMetadata(PasswordMetaDataName);
                 }
+                else
+                {
+                    logMethod("HostObject credentials not detected. Falling back to Docker credential retrieval.");
+                }
             }
         }
         return retVal;