Consider using tdlight User API

[JosXa]

There is now a modified version of the Bot API capable of running in user mode.
It would be a big advantage for integration tests to be able to load off session state handling to an API, immediately solving #18 and making the overall experience a lot easier.
However, Pyrogram is (and won't be) capable of interfacing with (the) REST APIs, so we'd need to think about rewriting or interfacing with aiogram instead.