Add options to automatically blocked users configuration

Problem to solve

Allow more customization to block automatically created users.

Currently with gitlab_rails['omniauth_block_auto_created_users'] enabled all new users are blocked and need to be manually blocked. It would be useful to have more options to specifically whitelist specific domains or patterns to not autoblock.

Perhaps something like:

gitlab_rails['omniauth_allow_auto_created_users'] = {
  domain: '*.domain'
}

Documentation

https://docs.gitlab.com/ee/integration/omniauth.html#initial-omniauth-configuration

Links / references

Internal ZD

added Category:User Management authentication oauth typefeature labels

added Manage [DEPRECATED] label

Setting gitlab-ce4116705 gitlab-ce10046105 based on gitlab-ce2677572 gitlab-ce4107687 gitlab-ce~3338737.

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Setting ~"group::access" based on authentication oauth.

added groupauthentication and authorization [DEPRECATED] label

mentioned in issue #212096 (closed)

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added sectiondev label

mentioned in issue #246438 (closed)

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mentioned in issue #261974 (closed)

mentioned in issue gitlab-org/quality/triage-reports#468 (closed)

mentioned in issue gitlab-org/quality/triage-reports#526 (closed)

added 1 deleted label and removed groupauthentication and authorization [DEPRECATED] label

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added to epic &5791

@hsutor Could this be an issue for ~"group::authentication and authorization"?

@lohrc Yes, this would be us! I'll change labels.

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That would be very helpful

Is it possible to exclude an OmniAuth provider from gitlab_rails['omniauth_block_auto_created_users']?

Say you have 'github' and 'saml', could you specify gitlab_rails['omniauth_block_auto_created_users'] = ['github']?

added devopsgovern sectionsec labels and removed devopsmanage sectiondev labels

added groupauthentication label and removed groupauthentication and authorization [DEPRECATED] label