Add more error

Author: Manikanta Nallagatla

src/WebJobs.Script.WebHost/Controllers/InstanceController.cs

@@ -41,7 +41,12 @@ public async Task<IActionResult> Assign([FromBody] HostAssignmentRequest hostAss
             if (string.IsNullOrEmpty(hostAssignmentContext.EncryptedContext) &&
                 (hostAssignmentContext?.AssignmentContext == null || hostAssignmentContext.AssignmentContext == null))
             {
-                return BadRequest("Assignment context and EncryptedContext is missing.");
+                return BadRequest("Atleast one of Assignment context and EncryptedContext needs to be set.");
+            }
+            if (!string.IsNullOrEmpty(hostAssignmentContext.EncryptedContext) &&
+                !(hostAssignmentContext?.AssignmentContext == null || hostAssignmentContext.AssignmentContext == null))
+            {
+                return BadRequest("Only one of Assignment context and EncryptedContext needs to be set.");
             }
 
             var debugMessage = (hostAssignmentContext.EncryptedContext.Length > 0) ? "ContextLength is : " + hostAssignmentContext.EncryptedContext.Length : "Using unencrypted assignment context";