healthchecks/hc/payments/admin.py

from django.contrib import admin
from .models import Subscription


@admin.register(Subscription)
class SubsAdmin(admin.ModelAdmin):

    list_display = ("id", "email", "customer_id",
                    "payment_method_token", "subscription_id", "plan_id")

    def email(self, obj):
        return obj.user.email if obj.user else None