Allow passing through psycopg.connect params in factories.postgresql()

I'd like to set `row_factory=psycopg.rows.dict_row` for the connection returned by the pytest fixture. 

Current workaround:
```py
@pytest.fixture(autouse=True)
def set_default_row_factory(client: psycopg.Connection):
    client.row_factory = psycopg.rows.dict_row
```