Session cookie fix

[ToasterChicken]

Summary

This is regarding Issue #2019

It adds persistent session features, and also the option for refreshing the current session before it expires while it's still valid (refresh window) and if it's beyond that window the session is invalid.

The default behavior without the new features should also remain the same was it was prior to the changes, every single requests results in a new session cookie.

I feel like there's possibly a much better way of doing this like being able to handle it all with in the call before the send_wrapper. However this is my first time delving into the ASGI framework so I'm not sure if I am able to obtain the new session data and compare it to the old session data only within the call and not have to make one cookie in call and another one with in send_wraper to resolve the current cookie and compare it to the new data.

Haven't added any tests to test_session.py yet, since I think this is a pretty large change and I can go ahead and work on that if this appears to be something that maybe accepted. The existing test suite passes however, and manually testing individual behaviors from the update work as expected.

There's no single change here, its a pretty big overall change to the middleware.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• Passes existing tests.
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[ToasterChicken]

I re-submitted thinking there was something else wrong. but no it's because I don't have the tests implemented for the new logic...

Anyways, I feel like discussing this before getting all into that maybe first step before going through all of that since it isn't an insignificant change to the middleware.

[ToasterChicken]

Will resubmit with the change suggested in the discussion.