Merge branch 'develop' into 'production'

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

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

...ffice/templates/backoffice/assembly_additionalfields.html

src/backoffice/templates/backoffice/assembly_basicdata.html

src/backoffice/templates/backoffice/assembly_detail.html

src/backoffice/templates/backoffice/assembly_edit.html

src/backoffice/views/assemblies.py

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

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

src/core/models/conference.py

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

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