detect if migrations have already been created using cli on server console

When i start using hasura cli to manage my migrations and by mistake if i switch to server console to modify schema / metadata, my whole migration workflow goes for a toss.

Adding the remaining migrations manually is one option but tedious.

But if the console served by the server can detect if migrations have already been created before (can be found using the `migration_settings` table inside `hdb_catalog`), then it should throw a warning asking for a confirmation to go ahead.