[Feature Request]: Stop using `Any` (statically-typed Pipeline) about beam

[dahlbaek]

While working on #3 I ran into

beam/sdks/rust/src/internals/serialize.rs

Lines 13 to 29 in 28b838e

	static SERIALIZED_FNS: Lazy<Mutex<HashMap<String, Box<dyn Any + Sync + Send>>>> =
	Lazy::new(|| Mutex::new(HashMap::new()));
	pub fn serialize_fn<T: Any + Sync + Send>(obj: Box<T>) -> String {
	let mut serialized_fns = SERIALIZED_FNS.lock().unwrap();
	let name = format!("object{}", serialized_fns.len());
	serialized_fns.insert(name.to_string(), obj);
	name
	}
	pub fn deserialize_fn<T: Any + Sync + Send>(name: &String) -> Option<&'static T> {
	let binding = SERIALIZED_FNS.lock().unwrap();
	let untyped = binding.get(name);
	let typed = match untyped {
	Some(x) => x.downcast_ref::<T>(),
	None => None,
	};

which made debugging somewhat tedious. As far as I can tell it's an unnecessary indirection 🤔 it seems to me a more idiomatic solution in Rust would be to make Transformations/Operators generic as needed so they can carry the closures directly, which should make it possible to remove a lot of the current usage of Box/Any. Do you agree @laysakura, or is there something I've misunderstood?

[laysakura]

@dahlbaek I definitely agree with you!

[laysakura]

Found out that statically-typed pipelines (including user-defined types) are unrealistic via:

• Description in #14
• #14 (comment)