Improper browser language handling in captive-portal

[KozlikCZ]

Describe the bug
I installed Czech language in PF and set Czech language (cs) in Firefox browser but only en_US lang works.

To Reproduce

1. Install cz language PO file from Transifex as described in the PF development guide.
2. Add the lang cs_CZ in files /usr/local/pf/Makefile, /usr/local/pf/html/pfappserver/root/src/globals/pfLocales.js, /usr/local/pf/lib/pf/web/constants.pm, /usr/local/pf/conf/documentation.conf.
3. Rebuid containers pfperl-api, httpd.admin_dispatcher, httpd.portal
4. Restart services pfperl-api, httpd.admin_dispatcher, httpd.portal
5. Set Czech language in Firefox browser - only 'cs'
6. Remove all language settings in PF GUI -> Connection Profile -> Captive Portal -> Languages
7. Refresh captive-portal pages in PF GUI -> Connection Profile -> Preview

Expected behavior
My browser language set: 1. cs, 2. en_US, PF language result set 1. en_US, 2. cs_CZ. PF evaluated general browser lang cs as closest lang cs_CZ with lower priority than exact lang en_US. This result set is better: 1. cs_CZ, 2. en_US with preserved priority. Czech language hasn't any variant and there is only cs language in Firefox. I made a patch - in attachment.

lang.patch.txt

PF:

• OS Linux, Debian 11.11
• PF 13.2 with all updates

Desktop (please complete the following information):

• OS Linux, Debian 12.9
• Browser Firefox 128.7.0esr (64 bits)

Thanks

Martin