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/accounts/middleware.py

@@ -0,0 +1,27 @@
+from django.shortcuts import redirect
+
+
+class PortalStaffMiddleware:
+    """Keep customer accounts out of the staff portal. Webhooks stay public."""
+
+    PORTAL_PREFIX = "/portal/"
+    WEBHOOK_INFIX = "/webhooks/"
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        path = request.path
+        if path.startswith(self.PORTAL_PREFIX) and self.WEBHOOK_INFIX not in path:
+            user = getattr(request, "user", None)
+            if (
+                user is not None
+                and getattr(user, "is_authenticated", False)
+                and not getattr(user, "is_staff", False)
+            ):
+                from django.apps import apps
+
+                if apps.is_installed("shop"):
+                    return redirect("account:home")
+                return redirect("public:home")
+        return self.get_response(request)