Add shopper accounts, reviews, tracking, and seed_demo (#9)

Closes #9. Shop-gated buyer accounts, purchase reviews, Stripe customer ids, shipment tracking, slim public contact form, and a template-neutral seed_demo command.

site/shop/admin.py

@@ -1,6 +1,6 @@
 from django.contrib import admin
 
-from shop.models import Order, OrderItem, Product
+from shop.models import Order, OrderItem, Product, ProductReview
 
 
 @admin.register(Product)
@@ -11,6 +11,13 @@ class ProductAdmin(admin.ModelAdmin):
     prepopulated_fields = {"slug": ("name",)}
 
 
+@admin.register(ProductReview)
+class ProductReviewAdmin(admin.ModelAdmin):
+    list_display = ("product", "user", "rating", "created_at")
+    list_filter = ("rating",)
+    search_fields = ("product__name", "user__email", "title")
+
+
 class OrderItemInline(admin.TabularInline):
     model = OrderItem
     extra = 0
@@ -21,4 +28,5 @@ class OrderAdmin(admin.ModelAdmin):
     list_display = ("number", "email", "amount", "status", "created_at")
     list_filter = ("status",)
     search_fields = ("number", "email", "customer_name")
+    raw_id_fields = ("user",)
     inlines = [OrderItemInline]