Duplicate CTMS records created during FxA email workflow

[robhudson]

Description

A workflow involving changes to primary and secondary emails in a Mozilla Account can lead to duplicate records in CTMS. This creates inconsistencies in how user data and subscriptions are represented.

Steps to Reproduce

1. Create a Mozilla Account using an email address userA@example.com.
   • This creates CTMS user 1 with emails.primary_email and fxa.primary_email set to userA@example.com.
2. Add a second email address userB@example.com as a secondary email but do not make it the primary email.
   • In CTMS, this is not recorded. It's only an FxA change at this point.
3. Use the secondary email address userB@example.com to sign up for a newsletter on the website.
   • This creates CMTS user 2 with emails.primary_email set to userB@example.com.
4. Go back to the Mozilla Account and make the secondary email userB@example.com the primary email.
   • For CTMS user 1 this updates fxa.primary_email to userB@example.com while keeping the emails.primary_email value of userA@example.com.
   • CTMS user 1's fxa.primary_email now conflicts with CTMS user 2's emails.primary_email.

Observed Behavior

• Two CTMS records are created:
  1. CTMS user 1 with:
     • emails.primary_email: userA@example.com
     • fxa.primary_email: userB@example.com
  2. CTMS user 2 with:
     • emails.primary_email: userB@example.com.

Steps to Reproduce - Alternate workflow

1. Create a Mozilla Account using an email address userA@example.com.
   • This creates CTMS user 1 with emails.primary_email and fxa.primary_email set to userA@example.com.
2. Add a second email address userB@example.com as a secondary email and make it the primary email.
   • In CTMS this updates fxa.primary_email to userB@example.com.
3. Use the email address userB@example.com to sign up for a newsletter on the website.
   • This creates CMTS user 2 with emails.primary_email set to userB@example.com.

Observed Behavior

• Two CTMS records are created:
  1. CTMS user 1 with:
     • emails.primary_email: userA@example.com
     • fxa.primary_email: userB@example.com
  2. CTMS user 2 with:
     • emails.primary_email: userB@example.com.

Expected Behavior

• There should be only one CTMS record for the user:
• To fix this issue, define and implement a solution to merge 2 contacts.

Additional Considerations

• The emails table includes a basket_token, which allows users to navigate to the preference center.
• If records are merged, take into consideration which basket_token remains functional so users can access the preference center.
• Perhaps a system notification email is sent notifying the user of the merge and providing the chosen basket token as a reference. The other basket token will result in a 404 from that point forward.