I am currently trying to add sip: links to online classrooms on Skype. At the moment, whenever I add sip: to the href of an <a> element, it gets stripped out. I discovered HTMLPurifier is doing this and tried setting 'sip => true' in /lib/htmlpurifier/HTMLPurifier/ConfigSchema/schema/URI.AllowedSchemes.txt
That still didn't work, and when testing the other enabled URIs in URI.AllowedSchemes.txt they also didn't work, with the exception of mailto. I also noticed caching is going on, so I tried purging the caches but no luck. So I'm wondering if anyone as experienced this or successfully enabled a specific URI prefix?