Redmine

The attached patch implements web hook support - to call / notify external services when something happens in Redmine.

While this patch just implements the issue create / update / delete events, it was built to be easily extended for lifecycle events of other entities.

Web hooks are defined at the user level, and always run in this users' context, regardless of who triggered the actual event. Events on issues a user cannot see will not trigger this users' configured hooks. The hook payload is JSON and has type (event), timestamp and data (the object involved) top level elements, using the existing issues/show API template for consistency to render the issue data inside data.

Each hook is defined for a list of events and projects. Whenever one of the events occurs in one of the projects, a POST request is sent to the configured URL with a payload depending on the event. Webhook signing with a pre-configured secret is implemented using the same algorithm GitHub uses .

This feature was developed and is in production use at Planio .

We'd very much like this to be integrated into Redmine, since it is really powerful when combined with platforms like Zapier or IFTTT. Zapier for example allows to define transformations (using Javascript) to change the JSON payload before triggering an action on another service and can therefore work as an adapter between Redmine and another service, even if the original payload format is not what the other service expects.

I rebased on current master, added a `use_webhooks` permission and also fixed some random test failures related to the caching of the IP blacklist configuration.