feat(jwt): add email claim to session JWT

[shentschel]

Description

This PR adds an email claim to the session JWT when the user has a primary email address. The claim contains the following fields:

• primary email address of the user
• Flag if the email address is a primary address
• Flag if the email address is verified

This PR also cleans up some unused stuff and refactors some error messages.

Closes: #1388