old_contents: from django.contrib import admin
  
  # Register your models here.
  from studygroups.models import Course, StudyGroup, StudyGroupSignup, Application
  
  class CourseAdmin(admin.ModelAdmin):
      pass
  
  class StudyGroupSignupInline(admin.TabularInline):
      model = StudyGroupSignup
  
  class StudyGroupAdmin(admin.ModelAdmin):
      inlines = [StudyGroupSignupInline]
  
  class StudyGroupSignupAdmin(admin.ModelAdmin):
      pass
  
  class ApplicationAdmin(admin.ModelAdmin):
      pass
  
  admin.site.register(Course, CourseAdmin)
  admin.site.register(Application, ApplicationAdmin)
  admin.site.register(StudyGroup, StudyGroupAdmin)
  admin.site.register(StudyGroupSignup, StudyGroupSignupAdmin)
  
new_contents: from django.contrib import admin
  
  # Register your models here.
  from studygroups.models import Course, StudyGroup, StudyGroupSignup, Application
  
  class StudyGroupSignupInline(admin.TabularInline):
      model = StudyGroupSignup
  
  class ApplicationInline(admin.TabularInline):
      model = Application.study_groups.through
      readonly_fields = ['user_name']
      def user_name(self, instance):
          return instance.application.name
      user_name.short_description = 'user name'
  
  class StudyGroupAdmin(admin.ModelAdmin):
      inlines = [
          #StudyGroupSignupInline,
          ApplicationInline,
      ]
  
  class StudyGroupSignupAdmin(admin.ModelAdmin):
      pass
  
  class CourseAdmin(admin.ModelAdmin):
      pass
  
  class ApplicationAdmin(admin.ModelAdmin):
      list_display = ('name', 'contact_method', 'created_at')
  
  
  admin.site.register(Course, CourseAdmin)
  admin.site.register(Application, ApplicationAdmin)
  admin.site.register(StudyGroup, StudyGroupAdmin)
  admin.site.register(StudyGroupSignup, StudyGroupSignupAdmin)
  
subject: Add applications to study groups