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/models.py

@@ -17,3 +17,19 @@ class RealtorProfile(TimeStampedModel):
 
     def __str__(self) -> str:
         return self.display_name or self.user.get_username()
+
+
+class CustomerProfile(TimeStampedModel):
+    """Shop-buyer profile. Card numbers stay on Stripe; we only keep the customer id."""
+
+    user = models.OneToOneField(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="customer_profile",
+    )
+    phone = models.CharField(max_length=32, blank=True)
+    shipping_address = models.JSONField(default=dict, blank=True)
+    stripe_customer_id = models.CharField(max_length=255, blank=True)
+
+    def __str__(self) -> str:
+        return self.user.get_username()