fix: IsDuplicatedEmail should filter out identities for the currentUser

[kangmingtay]

What kind of change does this PR introduce?

• Fixes Cannot change email to the same value of existing auth.identities record for non-"email" providers #1060, Users created with Phone provider (and with an email address added later) are unable to login via oAuth #988
• Allows one to pass in an optional currentUser into IsDuplicatedUser to exclude the user's identities when checking for duplicates
• This is optional because on signup / admin create user, there won't be a current user so it's guaranteed that any identities found belongs to a different user.

Current behaviour

• Currently, IsDuplicatedEmail only accepts an email and an aud and uses those fields to check if the auth.identities table has identities with the same email. When this is used in the context of updating a user's email (PUT /user), IsDuplicatedEmail will also include identities that belong to the current user.

[github-actions]

🎉 This PR is included in version 2.60.9 🎉

The release is available on GitHub release

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