Wake endpoint
A wake endpoint is an HTTP address WWKG calls before it tries to contact a cloud machine that may be asleep.
Some hosting platforms suspend idle machines to reduce resource usage. When new traffic arrives, the wake request gives the platform time to start the machine before WWKG opens its peer-to-peer connection. Always-on machines do not need a wake endpoint.
On Fly.io, WWKG derives the endpoint from FLY_APP_NAME. Other deployments
can set WWKG_WAKE_ENDPOINT to an absolute HTTP or HTTPS URL.
The endpoint should start the target machine and return promptly. It is not a health-check URL and should not perform the requested WWKG operation itself.