Implement payment backends and interaction

Advances #3 (closed)

aleksis/apps/tezor/tables.py

@@ -98,7 +98,7 @@ class InvoicesTable(tables.Table):
         text=_("View"),
     )
     print = tables.LinkColumn(
-        "get_invoice_by_pk",
+        "print_invoice",
         args=[A("id")],
         verbose_name=_("Print"),
         text=_("Print"),