* Add JSON response format to webhooks
Support JSON responses for all webhook endpoints: index, show, create,
update, destroy, and activation. Adds jbuilder views, updates controllers
to use respond_to, and documents the API in docs/API.md.
* Address PR review feedback
- Use distinct board ID in API docs webhook example
- Use render "webhooks/show" in activations controller for consistency
* Address PR review feedback from flavorjones
- Include webhook.board in cache key to avoid stale board data
- Use _url instead of _path for location header consistency
* Fix webhook create test to match Location header format
Use board_webhook_url instead of board_webhook_path since the controller
returns a full URL in the Location header.
* Fix board ID in Location header example in API docs
Use distinct board ID in the Location URL to match the JSON body example.
Rob Zolkos