Cache key "ez-user-xxxxxx@yyyy.zz-by-login" contains reserved characters {}()/\@:

Steps to reproduce:

• Create a user with an email address as username under admin group
• Use the same email address for the email field
• Try to log in with this new user

Error message:

Cache key "ez-user-xxxxxx@yyyy.zz-by-login" contains reserved characters {}()/\@:

Expected:
It should be possible to use an email address as a username. Removing @ from the reserved characters should be enough.