Returns or updates the cluster's maintenance schedule.
Returns 200 OK when the requested maintenance operation was performed successfully.
Returns 307 TEMPORARY_REDIRECT redirect to the leading master when current master is not the leader.
Returns 503 SERVICE_UNAVAILABLE if the leading master cannot be found.
GET: Returns the current maintenance schedule as JSON.
POST: Validates the request body as JSON and updates the maintenance schedule.
This endpoint requires authentication iff HTTP authentication is enabled.