Add Azure/EntraID route for SAML

[b-rowan]

Adds support for SAML via the optional azure extra. This can be configured with the config.auth.azure options.

[rettichschnidi]

Wow, that was fast. Great, thanks a lot! However, I am not (yet) in a position to actually test this. We (@easybe, @tsagadar , worst case... I) will need to talk to our IT department first.

[b-rowan]

It's actually not even ready yet, it will need some fixing, I think the requests I'm trying from the msal lib are probably not right, I will need someone with an actual AzureAD account to try them out and add the proper handling. For now this is just a button, some settings, some checks, and dependency handling.