message: refactor `CustomType`
diff: @@ -9,14 +9,14 @@ pub struct CustomType {
  opt_string: Option<String>,
  unsigned: u32,
  opt_unsigned: Option<u32>,
  - unsigned_8: u8,
  - unsigned_16: u16,
  - unsigned_32: u32,
  - unsigned_64: u64,
  - signed_8: i8,
  - signed_16: i16,
  - signed_32: i32,
  - signed_64: i64,
  + uint8: u8,
  + uint16: u16,
  + uint32: u32,
  + uint64: u64,
  + int8: i8,
  + int16: i16,
  + int32: i32,
  + int64: i64,
  opt_bigint: Option<BigInt>,
  bytes: Vec<u8>,
  opt_bytes: Option<Vec<u8>>,
  