TT#66577 Add foreign keys for 'sems_registrations'

New foreign keys:
- 'sub_id_ref' - towards 'subscriber.id'
- 'lcr_gw_ref' - towards 'lcr_gw.id'

Beforehand delete all alone subscriber_id's from the 'sems_registrations'
in case they for some reason exist, this will prevent us from .up script failure.

Change-Id: Ib225cc11771c9038c408f6c409d95a417e7ac311

db_scripts/diff/15690.down

@@ -0,0 +1,4 @@
+use kamailio;
+ALTER TABLE kamailio.sems_registrations
+  DROP FOREIGN KEY `sub_id_ref`,
+  DROP FOREIGN KEY `lcr_gw_ref`;

db_scripts/diff/15690.up

@@ -0,0 +1,9 @@
+use kamailio;
+
+SET autocommit=0;
+DELETE FROM `sems_registrations` WHERE `sems_registrations`.`subscriber_id` NOT IN (SELECT `id` FROM `subscriber`);
+COMMIT;
+
+ALTER TABLE `sems_registrations`
+  ADD CONSTRAINT `sub_id_ref` FOREIGN KEY (`subscriber_id`) REFERENCES `subscriber` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
+  ADD CONSTRAINT `lcr_gw_ref` FOREIGN KEY (`peer_host_id`) REFERENCES `lcr_gw` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;