Start a 9.0.x branch for Varbase Social Single Sign-On to work with Varbase ~9.0 and Drupal ~9.0

Problem/Motivation

Support Varbase ~9.0 and Drupal ~9.0
Manage all required modules to work under Drupal 9

Proposed resolution

Have two branches

• Branch 9.0.x : Support Drupal ~9.0 and Varbase ~9.0
• Branch 8.x-6.x : Limit the support to Drupal ~8.9 and Varbase ~8.8

Branch 9.0.x from varbase_auth 8.x-6.10 point