Bitbucket Server webhooks miss needs work => unapproved

Created by: eseliger

Currently, the webhooks by Bitbucket Server don't trigger when the review status is changed from "needs work" to "unapproved". The reason for that is, that we listen for PullRequestActivityEvents, not PullRequestEvents. That's what is reflected in the activity log, but for some reason BBS doesn't log unapproved after approved.

I think the completely correct behavior would be to not listen for the activity events but PR events in general and do proper filtering. This would require some adjustment to the code parsing the webhook payload also.