[CORD-3180] Setting app_id as mandatory and handling 409 error

Change-Id: Ie712d1e8e6bef402c63893f070ebb5de9f01e518
diff --git a/xos/synchronizer/models/models.py b/xos/synchronizer/models/models.py
new file mode 100644
index 0000000..9c01b5b
--- /dev/null
+++ b/xos/synchronizer/models/models.py
@@ -0,0 +1,35 @@
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from xos.exceptions import XOSValidationError
+
+from models_decl import ONOSApp_decl
+from models_decl import ONOSService_decl
+
+class ONOSApp(ONOSApp_decl):
+    class Meta:
+        proxy = True
+
+    def save(self, *args, **kwargs):
+
+        if self.url and not self.version:
+            raise XOSValidationError("If you specify and url, you also need to specify a version. ONOSApp:  %s" % self.name)
+
+        super(ONOSApp, self).save(*args, **kwargs)
+
+
+class ONOSService(ONOSService_decl):
+   class Meta:
+        proxy = True 
+