Resolve "New user flow for SSOing into a GitLab.com group"

What does this MR do?

Setup GDK

• Make sure you have an Ultimate license for your local instance.
• Enable the following feature flags via the Rails console (run rails c in gdk-ee/gitlab):
  • sign_up_on_sso
  • enforced_sso
  • group_managed_accounts
  • group_scim
• Follow gdk saml docs, adding he following changes to your gitlab.yaml file:

omniauth:
    providers:
      - { name: 'group_saml' }

• Enable SAML Single Sign On for one of your groups (e.g., gitlab-org):
  • Go to your group -> Settings -> SAML SSO
  • Setup SAML as follows

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/5292

https://gitlab.com/gitlab-org/gitlab-ee/issues/9375

CE port: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26578

What are the relevant issue numbers?

#5292 (closed)

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/9375

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

Closes #5292 (closed)