* DB changes
- Create a table for push topics NameTableStore
- Add a foreign key on subscriptions to normalize push topics
* Implement NameTableStore to normalize topics
* Update DB query joins to include topic from foreignkey
* Adapt code to use IDs instead of the actual topic
Bug: T261756
Change-Id: Ia7589f4a607993352d45b2dd3bcb3867d12d6e97
1) send apns topic when present in subscription metadata
2) check if subscription metadata is a valid JSON string
3) make epp_id column at echo_push_provider table auto_increment,
otherwise it will fail when trying to add a second row in the table
Bug: T259394
Change-Id: I785435e9f2d4ba9c14977d431d271f0fa2d0c795
