Name: event-polling-interval-declaration
Type: request
Purpose: >
  Declares the recommended interval for polling the event status
Response: receipt
Inherits: message
Elements:
  Signature: { required: true }
  From: { required: true }
  Event-Id: { required: true, type: identifier, class: event }
  Interval: { required: true, type: integer, min: 1, max: 300 }
Rejection-Codes:
  31: Sender is not authorized to declare polling interval
  41: Event does not exist