Investigate SSO GitLab.com SCIM for Okta

Now that we have auto member management through SCIM, there has been a lot of interest from prospects and customers to get this for their provider.

This is the issue for Okta.

Testing and relevant documentation will need to be updated, namely SCIM setup page

Likely blocked by supporting email as ID: https://gitlab.com/gitlab-org/gitlab-ee/issues/11540

Proposal

• Test what changes are required to support SCIM through Okta.
  • Likely includes https://gitlab.com/gitlab-org/gitlab-ee/issues/11540. See https://gitlab.com/gitlab-org/gitlab-ee/issues/5014#note_167732947 for some reports from customers.

This issue can be closed once we validate that our SCIM endpoints work via Okta and our documentation is up to date.

Other Links

Relevant comment by one user on testing via API: https://gitlab.com/gitlab-org/gitlab-ee/issues/5014#note_167732947