Bug: User emails table primary key too large

[Mistralys]

When importing the current pristine SQL, depending on the MySQL server settings, the primary key of the table user_emails is too large when using utf8mb4. To be future-proof, another primary key must be created.

Some solutions mention adding a column with a hash of the email address, and to use the hash in the primary key.

Relevant discussion here:

https://stackoverflow.com/questions/38806843/how-to-store-utf-8-email-addresses-in-a-unique-mysql-column-using-php