Database error occurs when inviting user whose email already exists but with a different case

[zpchavez]

When inviting a user, we check if the email already exists and if it does we do a reinvite. If it does not exist, we create a new user. The problem is we do the check against the email column instead of the email_lower_case column. So if we invite [email protected] and they exist in OIDC as [email protected], it will try to create a new user and then fail because the email_lower_case field will not be unique.