This is a pre-requisite for permissions syncing on ADO.

• New users should be able to sign up on Sourcegraph with Azure https://github.com/sourcegraph/sourcegraph/pull/47763
• Existing users should be able to connect their Azure account to Sourcegraph https://github.com/sourcegraph/sourcegraph/pull/47763/

Functionality tasks

• Handle username conflict if present by adding a suffix -1, -2 and so on until a non-conflicting username is found (Tracked in https://github.com/sourcegraph/sourcegraph/issues/47894)
• Handle value for default URL This is not needed as we do not expose URL as a config
• Implement a behaviour similar to allowOrgs or allowGroups - Standalone issue created: https://github.com/sourcegraph/sourcegraph/issues/48555
• Show Azure connection in account security page client/web: Fix regression in connected accounts for ADO #48184
• Show pretty icon in sign in page https://github.com/sourcegraph/sourcegraph/pull/47865
• If allowSignup is false, disable new signups to sourcegraph - Standalone issue created: https://github.com/sourcegraph/sourcegraph/issues/48557
• Check email verification behaviour (email != "" in code)
  • I've checked with the security team on Slack and they are okay with this assumption. Also we have the same behavior in Gitlab auth provider when we invoke GetAndSaveUser and similarly for GitHub we always mark email as verified.

Good to haves

• Tweak custom query params injection in OAuthContext (https://github.com/sourcegraph/sourcegraph/pull/48209#discussion_r1121613113)

/cc @ryphil