I've added database migration support. In summary:
* JPA migration is done with Liquibase
* Mongo migration is done in a similar way, but no 3rd party lib (Mongo is easier as
it's schema-less and single vendor)
* connectionsJpa and connectionsMongo will automatically update the database (if
databaseSchema = update)
For more details look at
https://github.com/keycloak/keycloak/blob/master/misc/UpdatingDatabaseSch...
If there's any issues let me know!