Bug 36612: Add public_read_list to Koha::Ticket

Bug 36612: Add public_read_list to Koha::Ticket

Without the public_read_list to define which fields should be accessible
from the public endpoints we will always return a 500 from the API on
otherwise successfull additions of tickets via the OPAC.

Test plan
1) Enable OPACCatalogConcerns
2) Login to the OPAC and "Report a concern"
3) Note the error message in the UI "There was an error when submitting
   your concern, please contact a librarian."
4) Confirm that the concern is actually created regardless
5) Apply the patch here and restart plack
6) Submit another 'Report a concern' and now note the success message
   "Your concern was successfully submitted."

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>