Bug 37204: (QA follow-up) Pass old_booking into GetPreparedLetter

Thinking about the future, some libraries may wish to use the
old_booking object details in their notice so I opt to pass it into
GetPreparedLetter here to support that.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Sponsored-by: Büchereizentrale Schleswig-Holstein <https://www.bz-sh.de/>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>

Koha/Booking.pm

@@ -167,7 +167,10 @@ sub store {
                     message_transport_type => 'email',
                     branchcode             => $pickup_library->branchcode,
                     lang                   => $patron->lang,
-                    objects                => { booking => $self },
+                    objects                => {
+                        old_booking => $old_booking,
+                        booking     => $self
+                    },
                 );
 
                 if ($letter) {