Add POST-method grade push with JSON data
Right now, the grade-push webhook is used by requesting an URL with the data in it. Because Tomcat rejectsSubmitted by Elmer van Chastelet on 19 September 2016 at 13:14
%2Fby default, WebDSL encodes these slashes, but the system invoking the webhook is unaware of this. This causes 404’s when the data contains a slash.