Add DAO function and endpoint for archiving email reply_to addresses

Added a new DAO function which archives email reply_to addresses by
setting archived to True. This raises a new type of error, an
ArchiveValidationError, if trying to archive a default reply_to address.

Added a new endpoint for archiving email reply_to addresses.

app/exceptions.py

@@ -6,3 +6,7 @@ class DVLAException(Exception):
 class NotificationTechnicalFailureException(Exception):
     def __init__(self, message):
         self.message = message
+
+
+class ArchiveValidationError(Exception):
+    pass