old_contents: from django.contrib import admin
  from .models import Member, RoomAssignment, FoodHandicaps
  
  # Register your models here.
  
  admin.site.register(FoodHandicaps)
  
  @admin.register(Member)
  class MemberAdmin(admin.ModelAdmin):
      list_display = ('first_name', 'last_name', 'gender', 'money_received', 'is_really_ersti', 'is_full_aged')
      list_filter = ('gender', 'money_received', 'is_really_ersti')
      fieldsets = (
          ('Ofahrt', {
              'fields': ('base',)
          }),
          ('Formale Daten', {
              'fields': ('first_name', 'last_name', 'gender', 'birth_date'),
          }),
          ('Verpflegung', {
              'fields': ('food_preference', 'food_handicaps'),
          }),
          ('Status', {
              'fields': ('money_received', 'is_really_ersti'),
          }),
          ('Sonstiges', {
              'fields': ('free_text',),
          }),
      )
  
  
  @admin.register(RoomAssignment)
  class RoomAssignmentAdmin(admin.ModelAdmin):
  
      def get_members(self, obj):
          return ", ".join([str(t) for t in obj.members.all()])
  
      get_members.short_description = "Zugeteilte Personen"
  
      list_display = ['room', 'get_members']
      fieldsets = (
          ('Ofahrt', {
              'fields': ('base',)
          }),
          (None, {
              'fields': ('room', 'members'),
          }),
      )
      pass
  
new_contents: from django.contrib import admin
  from .models import Member, RoomAssignment, FoodHandicaps
  
  # Register your models here.
  
  admin.site.register(FoodHandicaps)
  
  @admin.register(Member)
  class MemberAdmin(admin.ModelAdmin):
      list_display = ('first_name', 'last_name', 'gender', 'money_received', 'is_really_ersti', 'is_full_aged')
      list_filter = ('gender', 'money_received', 'is_really_ersti')
      fieldsets = (
          ('Ofahrt', {
              'fields': ('base',)
          }),
          ('Formale Daten', {
              'fields': ('first_name', 'last_name', 'gender', 'birth_date', 'email'),
          }),
          ('Verpflegung', {
              'fields': ('food_preference', 'food_handicaps'),
          }),
          ('Status', {
              'fields': ('money_received', 'is_really_ersti'),
          }),
          ('Sonstiges', {
              'fields': ('free_text',),
          }),
      )
  
  
  @admin.register(RoomAssignment)
  class RoomAssignmentAdmin(admin.ModelAdmin):
  
      def get_members(self, obj):
          return ", ".join([str(t) for t in obj.members.all()])
  
      get_members.short_description = "Zugeteilte Personen"
  
      list_display = ['room', 'get_members']
      fieldsets = (
          ('Ofahrt', {
              'fields': ('base',)
          }),
          (None, {
              'fields': ('room', 'members'),
          }),
      )
      pass
  
subject: fix #19