This method overrides django.db.backends.base.creation.BaseDatabaseCreation.get_test_db_clone_settings.
This method overrides django.db.backends.base.creation.BaseDatabaseCreation.test_db_signature.
This takes into account the special cases of ":memory:" and "" for SQLite since the databases will be distinct despite having the same TEST NAME. See https://www.sqlite.org/inmemorydb.html