Add ability to mark web hooks as disabled (BB-10998)

When you've added a third-party integration, it may be desirable to disable it for a period while not deleting it entirely.

There is a certain amount of overhead in signing into the third-party system, locating the endpoint URL and re-establishing the link; a simple on/off switch would a welcome addition.

A single switch to disable all integrations would also be a good stretch goal.