message: ProtoCommandValidator: add precision validation
diff: @@ -55,6 +55,20 @@ namespace shared_model {
  return aggregateErrors(
  "CreateAccount", {}, {validatePublicKey(ca.public_key())});
  }
  + case iroha::protocol::Command::kCreateAsset: {
  + const auto &ca = command.create_asset();
  + return aggregateErrors(
  + "CreateAsset",
  + {},
  + {[](auto precision) -> std::optional<ValidationError> {
  + if (precision < 0 or precision > 255) {
  + return ValidationError(
  + "Precision",
  + {"Precision should be within range [0, 255]"});
  + }
  + return std::nullopt;
  + }(ca.precision())});
  + }
  case iroha::protocol::Command::kRemoveSignatory: {
  const auto &rs = command.remove_signatory();
  return aggregateErrors(
  