Pending users should be able to request a new verification mail

[MatthiasBrodelet]

When a user registers an account and does not verify his account during the verification period he is basically stuck and a manual intervention from an admin is needed to resend the verification mail.

Would it be possible to let the registration, login and password reset endpoints return an error which points this out in order for us to show a descriptive message and a link to request a new verification mail?
We notice that users often try one of these forms and give up if there is no way out without contacting us.

Other methods are fine too.
The user just needs to be able to resolve this issue without admin intervention.