new_contents: from django.contrib import admin
  
  from agir.api.admin import admin_site
  from . import models
  
  
  @admin.register(models.SystemPayTransaction, site=admin_site)
  class SystemPayTransactionAdmin(admin.ModelAdmin):
      list_display = ('payment', 'person', 'status', 'webhook_calls')
      readonly_fields = ('payment', 'person', 'status', 'webhook_calls')
      fields = readonly_fields
      list_filter = ('status',)
      search_fields = ('payment__email', 'payment__person__emails__address')
  
      def person(self, obj):
          return obj.person
  
subject: add admin for systempay transaction