WebhookSender

Send a prepared webhook payload for the application.

Immediate webhooks are sent from the Reverb worker handling the event, and batches from the flush job, so implementations should hand the payload off promptly instead of performing the HTTP request themselves. Return only once the payload has been accepted, such as queued or stored, and throw when that fails: a returning call releases the batch's claim, while a failure leaves the batch to be sent again.