Implement Default for Extension

[nolanderc]

Motivation

When using an Extension we often have to wrap the inner value in an Arc (and some lock if we need mutability). If we then want to use our extension we need to write out Extension<Arc<Mutex<T>>> each time we want to use that T in a handler. This becomes tedious very quickly. Thus we introduce a type alias for that extension:

type MyExtension = Extension<Arc<Mutex<...>>>;

// which is used like:
async fn handler(ext: MyExtension) -> ... { ... }

With that type alias, it would be really nice if we could easily construct the Arc<Mutex<...>> type just by calling MyExtension::default(). However, Extension<T> does not implement Default, even though it is just a simple newtype wrapper around the inner T.

Solution

We just add an additional #[derive(Default)] to the Extension struct.

[davidpdrsn]

Makes sense!

Wanna add a note to the changelog as well?

[nolanderc]

Wanna add a note to the changelog as well?

Done!

[davidpdrsn]

Thanks!