fixed qr for members with umlaut

jdav_web/finance/models.py

@@ -522,13 +522,15 @@ class Transaction(models.Model):
         bic = iban.bic
 
         reference = self.escape_reference(self.reference)
-
+        
+        # also escaping receiver as umlaute are also not allowed here
+        receiver = self.escape_reference(f"{self.member.prename} {self.member.lastname}")
         return f"""BCD
 001
 1
 SCT
 {bic}
-{self.member.prename} {self.member.lastname}
+{receiver}
 {iban}
 EUR{self.amount}