Only show service email prefs to users with access

tests/models/test_services.py

tests/views/test_selfservice.py

tests/views/test_user.py

uffd/models/service.py

uffd/templates/selfservice/self.html

uffd/templates/service/show.html

uffd/templates/user/show.html

uffd/translations/de/LC_MESSAGES/messages.mo

uffd/translations/de/LC_MESSAGES/messages.po

uffd/views/selfservice.py

uffd/views/user.py