fix(serde): encode optional types as Some

[shekhirin]

Motivation

There are binary formats such as bincode that care whether an Option is serialized using serialize_some or just serialize, because they prepend the enum variant of Option as a starting byte.

The tests were passing because JSON doesn't care about this.

Solution

Serialize quantity::opt as Some when the value is Some.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

nit

[shekhirin]

It made me think, if that's a bug, do we want to have it on other modules too such as

alloy/crates/serde/src/num.rs

Lines 23 to 33 in cf9a98f

	pub mod u8_opt_via_ruint {
	use alloy_primitives::U8;
	use serde::{Deserialize, Deserializer, Serialize, Serializer};
	/// Serializes u64 as hex string
	pub fn serialize<S: Serializer>(value: &Option<u8>, s: S) -> Result<S::Ok, S::Error> {
	match value {
	Some(val) => U8::from(*val).serialize(s),
	None => s.serialize_none(),
	}
	}

[mattsse]

nice catch we should actually use the serialize some here, this doesn't matter for json but I guess it does for bincode