LTI 1.1 uses OAuth 1.0, which requires 'hostname', among other things,
as part of signature verification. When Moodle is run behind a reverse
proxy, $_SERVER['SERVER_NAME'] is an unreliable way to fetch hostname.
It isn't always equal to the external hostname but instead can contain
the local host, meaning the signature verification will fail. This
change replaces the use of $_SERVER vars with $FULLME - which already
takes this into account - to fix the signature verification.
Co-authored-by: Berengar W. Lehr <Berengar.Lehr@uni-jena.de>
Jake Dallimore
a44b66b5fc