Single Sign On using apache mod_auth_pubtkt

Created by: JosephKiranBabu

Enabled cookie-based authentication using apache mod_auth_pubtkt for 3 applications that required basic auth earlier - Syncthing, tt-rss and Repro.

mod_auth_pubtkt is currently configured to use the DSA algorithm and SHA1 for hashing the ticket contents. Though the original intention was to use RSA and SHA256, mod_auth_pubtkt had some kind of hard-coding to use DSA and SHA1. We're currently working on fixing the issue in the library. The configuration must be changed once the fixes are applied in mod_auth_pubtkt.