onelogin: use the /api/2/saml_assertion API

[rodmatos]

Replaces the use of the /api/1/saml_assertion with its successor. OneLogin has communicated that the /api/1/saml_assertion has been deprecated and should have been removed in Feb 2021.

Documentation for the /1/saml_assertion. Documentation for the new /2/saml_assertion.

[marcus-crane]

This seems kind of important! 😬 Thanks

[marcus-crane]

@wolfeidau

[narcistesa]

Any chance of getting this reviewed/merged? 🙏

[rodmatos]

@wolfeidau: sorry for the direct ping but any chance of getting this pull request reviewed?

[ElementSpanky]

This is pestering us as well, hopefully it'll get reviewed and merged soon!