use Database.request_session to prevent from losing auth

[JackWyj]

No description provided.

[JackWyj]

When passed (username, password) to Connection, i got Exception: Code: 194, e.displayText() = DB::Exception: Password required for user default. The auth is stored in self.request_session, but it isn't used to post request.

[JackWyj]

sorry, didn't notice the another PR #45 , it solved the same problem.

[vavrusa]

This seems like a better solution than rewriting DSN, do you mind rebasing?

[JackWyj]

@vavrusa seems it has been solved, and i have rebased mine, i have seen the updates about the problem. thx!