resend email-confirmation email feature for registration and email change

[lchristmann]

add the feature, that a user can himself request another confirmation email (in case it didn't make its way) in two places:

• when someone registers and awaits the email that shall confirm that he owns his provided email address
• when someone changes his email via "edit profile" and shall confirm that he owns the new email address he provided

[lchristmann]

✅ implemented for registration

After successful registration the View now shows a discretely styled button to request being sent another confirmation email:

In case of successful enqueuing of the email it will show a success message:

In case of failure enqueuing the email it will show a failure message and referral to the support:

This can be used an arbitrary number of times. When one resending failed, you can just request another resend, and succeed the next time. There's no end.

[lchristmann]

✅ implemented for registration

After successful save of profile with new email (email is not taken by another account yet):

When clicking on the button "(...) E-Mail erneut anfordern":

This can be done an arbitrary number of times, too.