Allow Setting Pinning Cookie Attributes

[dchukhin]

This pull request allows users to set the pinning cookie's 'Secure', 'HttpOnly', and 'SameSite' attributes by using settings, which are based on Django's CSRF_COOKIE_SECURE, CSRF_COOKIE_HTTPONLY, and CSRF_COOKIE_SAMESITE settings.
The defaults for these settings keep the current behavior: not Secure, not HttpOnly, and 'Lax' SameSite (currently, the SameSite attribute is unset, which should default to 'Lax' in browsers).

A part of this work also changes the PINNING_COOKIE and PINNING_SECONDS in multidb/middleware.py to be functions, so they can be tested more easily.

[tobiasmcnulty]

Hey @jbalogh, hope you are well! I just wanted to check to see if this change is something you would consider accepting at some point. (Full disclosure, @dchukhin is on my team at Caktus). We're happy to help in any way with merge and/or release. Thanks as always for the numerous Django packages we seem to find handy! 🙂

[diox]

Hey, I'm not @jbalogh but I can review that, sorry for not catching it earlier.

[diox]

Also: if you rebase/merge with master this will allow Github Actions to run, with updated Django/Python versions we want to support.

[Jdsleppy]

Hi @diox , I think these changes are what you were looking for. GitHub says you need to manually approve running CI on this PR because it's from a first-time contributor to this repository. Cheers!

[diox]

Awesome, thanks for doing this

[diox]

0.10 has been released with this change.