Implement payment backends and interaction

Advances #3 (closed)

aleksis/apps/tezor/models/invoice.py

@@ -46,6 +46,14 @@ class Invoice(BasePayment, PureDjangoModel):
     def get_purchased_items(self):
         return self.for_object.get_purchased_items()
 
+    def get_person(self):
+        if hasattr(self.for_object, "person"):
+            return self.for_object.person
+        elif hasattr(self.for_object, "get_person"):
+            return self.for_object.get_person()
+
+        return None
+
     class Meta:
         constraints = [
             models.UniqueConstraint(fields=["transaction_id", "group"], name="number_uniq_per_group")