This structure represents a directory.
t() :: %Acmex.Resource.Directory{ caa_identities: String.t(), key_change: String.t(), new_account: String.t(), new_nonce: String.t(), new_order: String.t(), revoke_cert: String.t(), terms_of_service: String.t(), website: String.t() }
new(String.t()) :: {:ok, t()} | {:error, String.t()}