Merge branch 'feature/activity_log' into 'develop'

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

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

src/backoffice/templates/backoffice/activitylog_card.html

...ce/templates/backoffice/assemblyteam_assembly_detail.html

src/backoffice/templatetags/c3assemblies.py

src/backoffice/views/assemblies.py

src/backoffice/views/assemblyteam.py

src/backoffice/views/events.py

src/backoffice/views/moderation.py

src/backoffice/views/projects.py

src/core/admin.py

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

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

src/core/management/commands/create_conference.py

...grations/0155_activitylogentry_delete_assemblylogentry.py

src/core/models/__init__.py

src/core/models/activitylog.py

src/core/models/assemblies.py

src/core/models/events.py

src/core/models/projects.py