Add possibility to set up a outgoing web hook per bundle

I found that there was an error when creating a new outgoing webhook, caused by $webhook_config->getEvents() possibly being empty, and crashing the array_index(). My tweaked patch is attached.

I discovered that the new for submit would crash when saving an incoming hook, since it does not have the new events. Modified patch applied.

ant1 → changed the visibility of the branch 3302284-add-possibility-to to hidden.

Not compatible with 3.x