Support querying for users based on old email addresses in some cases

When we are querying by email address, we should support looking for alternates in the database when there is no immediate match. We currently have an email history table for previously known email addresses that should help bridge this gap. As the email lookup is already an authenticated endpoint, I don't think we overall need to worry about server load in this case. This feature would likely add some latency for missing user accounts, and is only as accurate as the historic email table.

This also wouldn't account for noreply/alternate emails in 3rd party services like GitHub, and would be constrained to our system only.