Add a `migration_mode` flag to the `console` CLI options

When using the cli console to modify your metadata, you can turn off migration_mode with a little toggle switch. This is great for when you are managing your own schema and don't want hasura to touch anything except its own metadata.

The trouble is that this little toggle is stateful, so if you're running out of docker, you have to remember to flip that switch each time you spin up a container.

It'd be great to just have a flag you can pass:

hasura console --migration-mode false

or

hasura console --no-migrations

The work around at the moment is to either:

• use curl (or similar) to mimic the API call that does this:

curl -H 'Content-Type: application/json' -X PUT -d '{"name": "migration_mode", "value": "false"}' http://0.0.0.0:9693/apis/migrate/settings

• execute some SQL when you spin up your postgres container:

CREATE TABLE IF NOT EXISTS hdb_catalog.migration_settings (setting text not null primary key, value text not null);

INSERT INTO hdb_catalog.migration_settings (setting, value) VALUES ('migration_mode', 'false') ON CONFLICT ON CONSTRAINT migration_settings_pkey 

DO NOTHING;

(Thank you to the awesome support team, and especially @shahidhk for the required SQL.)