Use payments field for invoice number

aleksis/apps/tezor/models/invoice.py

@@ -28,7 +28,6 @@ class Invoice(BasePayment, PureDjangoModel):
     group = models.ForeignKey(
         InvoiceGroup, verbose_name=_("Invoice group"), related_name="invoices"
     )
-    number = models.CharField(verbose_name=_("Invoice number"))
 
     for_content_type = models.ForeignKey(ContetType, on_delete=models.SET_NULL)
     for_object_id = models.PositiveIntegerField()
@@ -39,5 +38,5 @@ class Invoice(BasePayment, PureDjangoModel):
 
     class Meta:
         constraints = [
-            models.UniqueConstraint(fields=["number", "token"], name="number_uniq_per_group")
+            models.UniqueConstraint(fields=["transaction_id", "group"], name="number_uniq_per_group")
         ]