@type t() :: %Inttegro.InitiateOTPRequest{
  async_delivery: boolean() | nil,
  message_template: String.t() | nil,
  purpose: String.t() | nil,
  recipient: String.t(),
  sender: String.t() | nil,
  service_name: String.t(),
  token_alphabet: String.t() | nil,
  token_alphabet_type: Inttegro.OTPAlphabetType.t() | nil,
  token_size: integer(),
  validity_duration_in_minutes: integer() | nil
}