Last tested: Aug 6, 2020
You currently has Google Authentication enabled on you instance and is changing email domains. You also wants to merge existing users accounts with your new Google Authentication email when they log in to be able to access their content, etc.
delete_google_auth_credential
Make sure that the Merge by Email
option is checked in the Google Authentication page in the Admin Panel, and strongly encourage you to run through the above steps with a test user to ensure it is working as expected.
Google Authentication Doc ref
Note: A colleague made an extension to help with this:
https://github.com/davidtamaki/admin_power_pack
Please note this is not officially supported resource - if you have a migration situation, please reach out filling an Issue in the git repo to get some help through it!
This content is subject to limited support.