Return a little more information in Issue webhook

**What does this MR do?**
When a webhook for issues is triggered, it should also return the
resource URL, and the action that was performed (ie: Was it reopened,
updated, opened or closed)

**Why is this MR needed?**
To make sure that services like Gitter can link to the proper issue from their UI, and also so they can show a better status.
I assume the intention here is to leave it open for others to add additional types later as opposed to try and implement all now?