Merge branch 'develop' into 'production'

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

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

...fice/templates/backoffice/account_activation_email-de.txt

...fice/templates/backoffice/account_activation_email-en.txt

src/backoffice/urls.py

src/backoffice/views/auth.py

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

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

src/core/tokens.py

src/core/views.py

src/plainui/forms.py

src/plainui/jinja2/plainui/assembly.html

src/plainui/jinja2/plainui/board.html

src/plainui/jinja2/plainui/board_edit.html

src/plainui/jinja2/plainui/board_private.html

src/plainui/jinja2/plainui/components/function_btns.html

src/plainui/jinja2/plainui/components/list_events.html

src/plainui/jinja2/plainui/components/three_cards.html

src/plainui/jinja2/plainui/fahrplan.html

src/plainui/jinja2/plainui/header.html