{"type":"topic-changed",
 "change":{"project":"project-name",
           "branch":"branch-name",
           "topic":"topic-name",
           "id":"Ideadbeefdeadbeefdeadbeefdeadbeefdeadbeef",
           "number":"123456",
           "subject":"Commit message subject",
           "owner":{"name":"Owner Name",
                    "email":"owner@example.com"},
           "url":"http://review.example.com/123456"},
 "changer":{"name":"Changer Name",
            "email":"changer@example.com"},
 "oldTopic":"old-topic"}
