Enhancement: add ASN to consume rejection message

When not consuming a document since its ASN collides with an already existing one,
make the ASN part of the message to make it easier for the user to find out which
document causes the collision.

src/documents/consumer.py

@@ -368,7 +368,7 @@ class Consumer(LoggingMixin):
         if Document.objects.filter(archive_serial_number=self.override_asn).exists():
             self._fail(
                 ConsumerStatusShortMessage.ASN_ALREADY_EXISTS,
-                f"Not consuming {self.filename}: Given ASN already exists!",
+                f"Not consuming {self.filename}: Given ASN {self.override_asn} already exists!",
             )
 
     def run_pre_consume_script(self):