Release 1.15.0

[rayluo]

• New feature: Now both initiate_auth_code_flow() and acquire_token_interactive() accept a new optional parameter max_age which is the allowable elapsed time in seconds since the last time the End-User was actively authenticated. If the elapsed time is greater than this value, Microsoft identity platform will actively re-authenticate the End-User. (#381, #389)
• Improvement: MSAL will now automatically utilize a backup authentication system, to provide better resiliency. (#376, #395, #409)
• Improvement: Previously, acquire_token_interactive() was not able to be aborted by CTRL+C when running on Windows. It is now fixed. (#393, #404)
• Bugfix: The http cache feature shipped in #379 came with an unexpected side effect to slow down the Device Code Flow. Now fixed. (#408, #410)

PS: Not contained in this PR, but we also manually squeezed in the change of adopting cryptography 35.0.0, so it will also be shipped in MSAL Python 1.15.0. (#414)

[rayluo]

Note: The 2 messages above were from an earlier conversation on a specific commit. It turns out github would somehow render them here in this release PR. We have resolved that offline. This PR is ready to ship.