Bug 24673: Add CSRF token support to opac-messaging.pl

Bug 24673: Add CSRF token support to opac-messaging.pl

This patch adds CSRF token support to opac-messaging.pl,
which allows users to manually update their messaging preferences,
but prevents bad actors from tricking people into updating their
preferences from cross-site requests.

Test plan:
0. Set SMSSendDriver global system preference to "Test" if unset
1. Log into the OPAC
2. Navigate to a URL in your browser like the following:
http://localhost:8080/cgi-bin/koha/opac-messaging.pl?modify=yes
&1=email&digest=1&2-DAYS=5&2=email&digest=2&4=email&SMSnumber=0444444444
3. Observe that the preference and SMS number update

4. Apply the patch

5. Navigate to a URL in your browser like the following:
http://localhost:8080/cgi-bin/koha/opac-messaging.pl?modify=yes
&1=email&digest=1&2-DAYS=5&2=email&digest=2&4=email&SMSnumber=0444444444
6. Observe that you get an error message of "Wrong CSRF token" instead
of the previous behaviour
7. Navigate to a URL in your browser like the following:
http://localhost:8080/cgi-bin/koha/opac-messaging.pl
8. Update "Advance notice" to 3 and update "SMS number" to 61111111111
9. Observe that the "Advance notice" and "SMS number" fields update
correctly

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Joy Nelson <joy@bywatersolutions.com>