Bug 31626: Add letter id to the message queue table

Bug 31626: Add letter id to the message queue table

It can be useful to know exactly what template was used to generate a notice. To this end, it would be useful to store the letter id as a foreign key in the message queue table.

Test Plan:
1) Apply this patch
2) Run updatedatabase.pl
3) Restart all the things!
4) Run an action that will send a notice to a patron
5) Note the letter id is now in the message_queue table for that notice!

Signed-off-by: Andrew Fuerste-Henry <andrewfh@dubcolib.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>