Enable users to voluntarily add email to account to alert them when their Stamps expire

[lebraat]

User Story:

As a user
I want to voluntarily receive emails when my Passport Stamps or onchain attestations expire
So that I can quickly update my score to ensure I always qualify for partner programs.

Acceptance Criteria

GIVEN a user who has voluntarily added their email to Passport
WHEN a Stamp or onchain attestation expires
THEN they receive an email a week in advanced to let them know that their Passport is expiring

Open Questions:

Where will users add their email?
What specific types of email notifications could we enable?
Should we explore text, telegram, or XMTP notifications as well?

Assumptions:

Users will be willing to add their email address or other contact information to be notified
This will increase the number of quarterly active users dramatically