Add skeleton query validation endpoint

Add a skeleton implementation of a query validation endpoint to allow
partners to begin implementation.

Part of work for #2585

web-services/query/src/main/java/datawave/webservice/query/runner/QueryExecutorBean.java

@@ -853,7 +853,7 @@ public GenericResponse<String> planQuery(@Required("logicName") @PathParam("logi
         QueryData qd = validateQuery(queryLogicName, queryParameters, null);
 
         GenericResponse<String> response = new GenericResponse<>();
-        
+
         Query q = null;
         AccumuloClient client = null;
         AccumuloConnectionFactory.Priority priority;
@@ -2996,7 +2996,7 @@ private void updateQueryParams(Query q, String queryLogicName, String query, Dat
             q.setParameters(params);
         }
     }
-    
+
     /**
      * @param queryLogicName
      *            the logic name
@@ -3006,16 +3006,17 @@ private void updateQueryParams(Query q, String queryLogicName, String query, Dat
      */
     @POST
     @Produces({"application/xml", "text/xml", "application/json", "text/yaml", "text/x-yaml", "application/x-yaml", "application/x-protobuf",
-                    "application/x-protostuff"})
+            "application/x-protostuff"})
     @Path("/{logicName}/validateQuery")
     @Interceptors({RequiredInterceptor.class, ResponseInterceptor.class})
     @Timed(name = "dw.query.validateQuery", absolute = true)
     public GenericResponse<String> validateQuery(@Required("logicName") @PathParam("logicName") String queryLogicName,
                     MultivaluedMap<String,String> queryParameters) {
         GenericResponse<String> response = new GenericResponse<>();
-        throw new DatawaveWebApplicationException(new UnsupportedOperationException("Query validator coming soon."), response, 501);
+        response.setMessages(Collections.singletonList("Query validator coming soon."));
+        throw new DatawaveWebApplicationException(new UnsupportedOperationException("Query validator not implemented"), response, 501);
     }
-    
+
     /**
      * <strong>Administrator credentials required.</strong> Returns list of queries for some other user
      *