Implement Asynchronous Authenticate Method

[CristopherH95]

This PR resolves #284. The primary changes are as follows:

1. asgiref is added to the install_requires in setup.py. This is done because the sync_to_async and async_to_sync functions are provided from asgiref 2.0.0 onward. Django distributions with async support automatically install asgiref, so the vast majority of the time this dependency should already be available.
2. A aauthenticate method is implemented in LDAPBackend, which runs a simple async wrapper around ldap.authenticate called run_authentication_async.
3. Adds a test testAuthenticateAsyncRunner, which checks that run_authentication_async calls ldap.authenticate as expected.

[CristopherH95]

@etianen looking into the failed check here, it looks like the problem may be related to versions of Python less than 3.9 not being available for the latest Ubuntu version (related issue I found: actions/setup-python#962). Should the action workflow be updated?

[CristopherH95]

@etianen just wanted to follow up on this and see if you have any thoughts.

[etianen]

I'm so sorry! I missed your comment from May! 😱

Please do update the matrix. Only supporting 3.9+ makes total sense. We can add in up to 3.13 in their place.

[CristopherH95]

I'm so sorry! I missed your comment from May! 😱

Please do update the matrix. Only supporting 3.9+ makes total sense. We can add in up to 3.13 in their place.

No worries! Sounds good, I can work on adding that to the PR.

[CristopherH95]

@etianen The matrix is updated with Python versions up to 3.12. There was a little trial-and-error on my part to get it working right, but it looks like all checks work as expected now. Let me know if there's anything else that should change!

[etianen]

Lovely job!

[etianen]

Released as v0.16.0!