Bug 11575 - OPACBaseURL sometimes set by ENV variable and not system preference

Bug 11575 - OPACBaseURL sometimes set by ENV variable and not system preference

This patch changes how the OPACBaseURL parameter gets set in the subroutine
get_template_and_user in Auth.pm.

Currently, it's being set by the $ENV{'SERVER_NAME'} variable. In many
cases, this will probably match the URL that the user uses to access a
page. However, this causes problems with reverse proxies.

There are ways to compensate for proxy servers (such as inspecting
other variables set by the web server), but such a solution seems
a bit convoluted...especially since we already use the system preference
OPACBaseURL in many other parts of Koha.

We probably shouldn't be passing OPACBaseURL from Auth.pm at all, and
instead use the Koha TT plugin and using_https param to determine
protocol. However, that's outside the scope of this bug/patch.

This patch is just meant to fix an existing bug.

I did leave the $ENV{'SERVER_NAME'} as a full back if OPACBaseURL isn't
set, but that's it.

_TEST PLAN_

Before applying:

1) Clear your OPACBaseURL preference
2) Perform a search in the OPAC
3) Click on or hover over the orange RSS icon
4) Note that the URL used for the RSS links is either:
  a) The same URL you used to access Koha (no reverse proxy)
  b) The ServerName from your Koha apache conf which isn't the
  same URL you used to access Koha (reverse proxy)
5) Add an OPACBaseURL that isn't the same as the actual OPAC URL
6) Note that the OPACBaseURL system preference has no effect here

After applying the patch:

7) Refresh the page
8) Note that the URL you see now is actually the OPACBaseURL system
preference that you set
9) Clear your OPACBaseURL system preference
10) Refresh your search page
11) Note that the URL has reverted back to the URL that you saw before
(either the original Koha site URL or the Koha ServerName defined
in Apache and not the URL of the proxy)

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>