SSO - Contrib dependency evaluation

[sherakama]

The Drupal 7 version of simplesamlphp_auth did not allow for enough flexibility to accomplish the goals we set out so we adopted it as a submodule of this project and re-wrote the parts that made sense to us.
See:

• https://github.com/SU-SWS/stanford_ssp/tree/7.x-2.x/modules/stanford_simplesamlphp_auth
• https://www.drupal.org/node/2745089

Evaluate wether or not the D8 version is stable and functional enough for this project to depend on or wether we will need to adopt/patch/contribute-to the contrib module.

[sherakama]

At first review it appears we will be able to go forward with using the contrib module from Drupal 8.