I have changed my email recently, and would like commits and mails from the old address to click through to my account even when registered to the new address.

This could be accomplished by allowing registering email aliases to an account, with the main account email being your current one.

The implementation should update the profile page to show a "primary" email address, with a link to "manage alternates". The second page should have a UI for adding new email addresses (or removing them) and selecting which is your primary address.

Adding a new alternate email address shouldn't kick in properly until you've answered a confirmation email.

Rules around global uniqueness of each email address still apply.

Further changes will be necessary to update the API with your alternate email addresses (both Python & GraphQL unless GQL webhooks are done in time), then updating downstream services to (1) store the alternates and (2) take them into account where appropriate to map email addresses to users.