Name: voting-definition
Type: request
Purpose: >
  Defines ("creates") a new voting.
Response: voting-definition-confirmation
Inherits: message
Elements:
  Signature: { required: true }
  From: { required: true }
  Event-Id: { required: true, type: identifier, class: event }
  Voting-Data: { required: true, type: object, class: voting }
Rejection-Codes:
  21: Incomplete voting data
  22: Invalid period start
  23: Invalid period end
  24: Voting with that name already exists
  31: Sender is not authorized to define voting
  41: Event does not exist