Add support for serialize_with and deserialize_with

[banool]

Hey, imagine I have code like this:

struct MyThing {
    my_other_thing: MyOtherThing
}

struct MyOtherThing {
    bytes: HexEncodedBytes,
}

struct HexEncodedBytes(Vec<u8>);

As it is now, you can't impl NewType on HexEncodedBytes as it doesn't impl ToHeader. That's not important though, imagine I want to make my API return HexEncodedBytes as a string like 0x32434. To get around this, I have to make 2 new structs: MyThingWrapper, MyOtherThingWrapper, and then a new newtype that for example encodes the Vec<u8> in some other way (a string, b64, etc). On top of that, I have to impl From<MyThingWrapper> for MyThing and all of the other types too.

As you can see, this ends up being a lot of additional wrapping code. Instead, what I'd like to do this this:

struct MyThing {
    my_other_thing: MyOtherThing
}

struct MyOtherThing {
    #[oai(serialize_with = "my_serializer", deserialize_with = "my_deserializer")]
    bytes: HexEncodedBytes,
}

struct HexEncodedBytes(Vec<u8>);

fn my_serializer(value: Vec<u8>) -> String {
    // convert
}

fn my_deserializer(value: String) -> Vec<u8> {
    // convert
}

Either that, or just pass in a serializer. With this, the spec should say that this field is a String, not a Vec<u8>.

Is there some way we could add this feature?

Thanks!

[banool]

Okay I'm digging deeper into a better way to do this, and I'm currently impling Type, ParseFromJSON, etc. on my own for my types. This is working fairly well so far but the moment I get to a type I don't own, I struggle. This type is a newtype so I can't impl remote either. Perhaps including remote as part of the ask in #320 would be a solution to this part of the problem.

[banool]

I'm going to close this for now, I don't think this is a well-thought-out suggestion as it is.

[BatmanAoD]

For future readers, serialize_with and deserialize_with were added in #749.