Support for psycopg2 client

[watarukura]

I want to use redash without PostgreSQL backend.
redash use psycopg2 for PostgreSQL driver.
I would be very happy if postlite supports psycopg2.

Here is redash log, use postlite instead of postgres.

 [2023-02-25 11:23:55,763] ERROR in app: Exception on /login [GET]
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1982, in wsgi_app
     response = self.full_dispatch_request()
   File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1614, in full_dispatch_request
     rv = self.handle_user_exception(e)
   File "/usr/local/lib/python2.7/site-packages/flask_restful/__init__.py", line 271, in error_router
     return original_handler(e)
   File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1517, in handle_user_exception
     reraise(exc_type, exc_value, tb)
   File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1612, in full_dispatch_request
     rv = self.dispatch_request()
   File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1598, in dispatch_request
     return self.view_functions[rule.endpoint](**req.view_args)
   File "/usr/local/lib/python2.7/site-packages/flask_limiter/extension.py", line 442, in __inner
     return obj(*a, **k)
   File "/app/redash/handlers/authentication.py", line 147, in login
     if current_org == None and not settings.MULTI_ORG:
   File "/usr/local/lib/python2.7/site-packages/werkzeug/local.py", line 365, in <lambda>
     __eq__ = lambda x, o: x._get_current_object() == o
   File "/usr/local/lib/python2.7/site-packages/werkzeug/local.py", line 302, in _get_current_object
     return self.__local()
   File "/app/redash/authentication/org_resolving.py", line 18, in _get_current_org
     g.org = Organization.get_by_slug(slug)
   File "/app/redash/models/organizations.py", line 33, in get_by_slug
     return cls.query.filter(cls.slug == slug).first()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2895, in first
     ret = list(self[0:1])
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2687, in __getitem__
     return list(res)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2995, in __iter__
     return self._execute_and_instances(context)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 3016, in _execute_and_instances
     close_with_result=True)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 3025, in _get_bind_args
     **kw
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 3007, in _connection_from_session
     conn = self.session.connection(**kw)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1035, in connection
     execution_options=execution_options)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1040, in _connection_for_bind
     engine, execution_options)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 409, in _connection_for_bind
     conn = bind.contextual_connect()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2123, in contextual_connect
     self._wrap_pool_connect(self.pool.connect, None),
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2162, in _wrap_pool_connect
     e, dialect, self)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1476, in _handle_dbapi_exception_noconnection
     exc_info
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 265, in raise_from_cause
     reraise(type(exception), exception, tb=exc_tb, cause=cause)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 2158, in _wrap_pool_connect
     return fn()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 400, in connect
     return _ConnectionFairy._checkout(self)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 788, in _checkout
     fairy = _ConnectionRecord.checkout(pool)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 529, in checkout
     rec = pool._do_get()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 1193, in _do_get
     self._dec_overflow()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
     compat.reraise(exc_type, exc_value, exc_tb)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 1190, in _do_get
     return self._create_connection()
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 347, in _create_connection
     return _ConnectionRecord(self)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 474, in __init__
     self.__connect(first_connect_check=True)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line 671, in __connect
     connection = pool._invoke_creator(self)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 106, in connect
     return dialect.connect(*cargs, **cparams)
   File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 412, in connect
     return self.dbapi.connect(*cargs, **cparams)
   File "/usr/local/lib/python2.7/site-packages/psycopg2/__init__.py", line 130, in connect
     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
 OperationalError: (psycopg2.OperationalError) server didn't return client encoding (Background on this error at: http://sqlalche.me/e/e3q8)
 [2023-02-25 11:23:55,772][PID:14][INFO][metrics] method=GET path=/login end

Here is my investigation repo.
https://github.com/watarukura/redash-postlite
Clone and docker compose up and open http://localhost, you can see error log.