Merge branch 'feature/under-construction' into 'develop'

src/plainui/jinja2/plainui/under_construction.html.j2

src/plainui/locale/de/LC_MESSAGES/django.po

src/plainui/locale/en/LC_MESSAGES/django.po

src/plainui/urls.py

src/plainui/views/auth.py

src/plainui/views/dereferrer.py

src/plainui/views/general.py

src/plainui/views/personal_messages.py

src/plainui/views/report.py

src/plainui/views/user_profile.py

src/plainui/views/utils.py