The webhook activation controller was using account-scoped lookup
instead of board-scoped lookup, allowing users to reactivate webhooks
on boards they don't have access to.
This was an oversight when board-scoping was added to the main webhooks
controller - the activations controller was missed in that update.
The fix adds the BoardScoped concern to properly restrict webhook
activation to boards the user has explicit access to.
Jeremy Daer
4efa4da809