Physical Interface can belong to only one Virtual Port Group

partial-jira-bug: CEM-15158

A physical-interface object can not be part of two different VPGs
This change verifies incoming PI that it do not belong to other VPGs
and throws BadRequest if given PI belong to other VPG.

In current implementation, this validation happens at VMI resource
which will be retried in next coming changes

src/config/api-server/vnc_cfg_api_server/resources/virtual_port_group.py

@@ -199,6 +199,31 @@ def update_physical_intf_type(cls, obj_dict=None,
         to_be_added_pi_uuids = list(set(new_uuid_list) - set(old_uuid_list))
         to_be_deleted_pi_uuids = list(set(old_uuid_list) - set(new_uuid_list))
 
+        # ensure this PI do not belong to other VPGs
+        pis_attached_to_vpg = {}
+        for pi_uuid in to_be_added_pi_uuids:
+            ok, pi_obj_dict = db_conn.dbe_read(
+                obj_type='physical-interface',
+                obj_id=pi_uuid,
+                obj_fields=['virtual_port_group_back_refs'])
+            if not ok:
+                return ok, (400, pi_obj_dict)
+            vpg_refs = pi_obj_dict.get('virtual_port_group_back_refs')
+            if vpg_refs:
+                pis_attached_to_vpg[pi_uuid] = vpg_refs
+        if pis_attached_to_vpg:
+            vpg_uuid = obj_dict.get('uuid')
+            msg = ""
+            for pi, vpgs in pis_attached_to_vpg.items():
+                for vpg in vpgs:
+                   msg += (
+                       'PI (%s) VPG-UUID (%s) VPG-FQNAME (%s); ' % (
+                       pi, vpg['uuid'],  ":".join(vpg['to'])))
+            return (
+                False,
+                (400, "physical interfaces already added at other VPGs can not"
+                      " be attached to this VPG (%s): %s" % (vpg_uuid, msg)))
+
         for pi_uuid in to_be_added_pi_uuids or []:
             try:
                 api_server.internal_request_update(