integrate suggestions from MR !734 review

src/api/views/maps.py

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

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

src/backoffice/templates/backoffice/map_floor_form.html

src/backoffice/templates/backoffice/map_floor_list.html

src/backoffice/templates/backoffice/map_poi_form.html

src/backoffice/urls.py

src/backoffice/views/map.py

src/core/admin.py

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

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

src/core/migrations/0118_map.py

src/core/models/__init__.py

src/core/models/assemblies.py

src/core/models/map.py

src/core/translation.py