Subscribe to events (MCP Events)

Creates or refreshes an MCP Events webhook subscription, as the Timesheet MCP server forwards events/subscribe. A subscription is identified by the event, its arguments and the callback URL: the same request again refreshes it and replaces its secret. The callback has to answer a signed verification challenge before the first delivery. Deliveries use Standard Webhooks signatures with the secret the caller supplied, and the subscription lapses at refreshBefore unless refreshed.