Bug 27860: Add message_id param to SendQueuedMessages

Bug 27860: Add message_id param to SendQueuedMessages

We could use C4::Letter::GetMessage, but the query in
_get_unsent_messages join on borrowers and return the branchcode.
To prevent any regressions it's preferable to not modify
SendQueuedMessages.

Ideally we obviously need a Koha methods to have better and clean code..

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>