Let a user create a db.
kitt=# \du
List of roles
Role name | Attributes | Member of
-------------+------------------------------------------------------------+-----------
kitt | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
burble_dev | | {}
kitt=# alter user burble_dev createdb;
ALTER ROLE
kitt=# \du
List of roles
Role name | Attributes | Member of
-------------+------------------------------------------------------------+-----------
kitt | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
burble_dev | Create DB | {}