Add support for login with Facebook OAuth

What does this MR do and why?

Describe in detail what your merge request does and why.

Add support for OAuth login with Facebook.

Variable values were set with https://gitlab.com/gitlab-org/quality/engineering-productivity-infrastructure/-/merge_requests/392. Facebook username was updated in https://gitlab.com/gitlab-org/quality/engineering-productivity-infrastructure/-/merge_requests/411)

Required for: gitlab!125514 (merged)

Related issue: gitlab-org/quality/testcases#3979 (closed)

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