Investigate: `Module::init()` should be type-safe

[plafer]

Currently, Module::init() takes a json object as input. We should investigate how to make this type-safe.

A rough sketch for a possibility would be:

trait Module {
    type InitData;

    fn init(&mut self, init_data: Self::InitData);
}

[romac]

Why not just take Self::InitData directly? If the caller already has a value of type Self::InitData then they won't be able to pass it to init because afaik &T does not implement Into<T>, or if it does it will delegate to clone.

[plafer]

Yep makes a lot more sense. Updated the description.

Although another alternative that might be best is to pass it by reference, and potentially have type InitData: Clone;?

[romac]

I don't see the upside of passing it by reference. If you know you will need ownership of the data, I would just pass an owned value and leave to the caller to clone it if needed.

[plafer]

It wasn't clear to me if the callee would need ownership, but I double-checked in the bank module and we indeed require ownership. We can leave it as is then!