* users can set up hooks for issue creation, update and deletion events, for any number of projects
* hooks run in the context of the creating user, and only if the object in question is visible to that user
* the actual HTTP call is done in ActiveJob
* webhook calls are optionally signed the same way GitHub does
Patch by Jens Krämer (user:jkraemer).
git-svn-id: https://svn.redmine.org/redmine/trunk@24034 e93f8b46-1217-0410-a6f0-8f06a7374b81
