Merge branch 'feature/fahrplan_assembly_sos' into 'develop'

src/backoffice/views/events.py

src/core/models/conference.py

src/core/utils.py

src/plainui/jinja2/plainui/base.html

src/plainui/jinja2/plainui/fahrplan.html

src/plainui/jinja2/plainui/my_fahrplan.html

src/plainui/jinja2/plainui/public_fahrplan.html

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

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

src/plainui/styles/components/_fahrplan.scss

src/plainui/tests.py

src/plainui/views.py