message: add size hint
diff: @@ -397,7 +397,7 @@ impl CryptoCommandExecutor {
  cek: &chacha20poly1305_ietf::Key,
  receiver_list: Vec<String>,
  ) -> IndyResult<String> {
  - let mut encrypted_recipients_struct : Vec<Recipient> = vec![];
  + let mut encrypted_recipients_struct : Vec<Recipient> = Vec::with_capacity(receiver_list.len());
  for their_vk in receiver_list {
  //encrypt sender verkey
  