Name: event-close-declaration
Type: request
Purpose: >
  Declares event as closed and prevents further registrations
Response: event-details
Inherits: message
Elements:
  Event-Id: { required: true, type: identifier, class: event }
Rejection-Codes:
  31: Sender is not authorized to close event
  41: Event does not exist
  42: Event has not been opened yet
  43: Event has been closed already