Sync OAuth Primary Email to d_b_users Table

Is your feature request related to a problem? Please describe

When working with customers in support there are time when I want to verify them by searching the email address that submitted the support ticket with what we have in our database (to ensure they match). However there are times when a customer updates their primary email address at their SCM. This causes the value store in the d_b_users table to become "de-synched".

Describe the behaviour you'd like

If the customer does change their primary email address at their SCM we should pull in that update so that it matches what we store and use when searching by email address at /admin/users.

Describe alternatives you've considered

Ask the user to recreate the ticket for the appropriate email address. This doesn't always work as they may no longer have access to the original email address as an example.

Additional context

N/A

Front conversations

Start by tracing how OAuth or SCM user data is written to the d_b_users table and how email search is handled at /admin/users. Confirm which primary-email changes must be synchronized and identify the relevant integration entry point; done means the stored email matches the SCM value after an update and remains searchable in /admin/users.