This adds `StreamBody` which converts a `Stream` of `Bytes` into a `http_body::Body`.
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As suggested by Kestrer on Discord it would make sense for axum to provide different kinds of body types other than `Empty`, `Full`, and `hyper::Body`. There is also some talk about [splitting up `hyper::Body`](https://github.com/hyperium/hyper/issues/2345) so this can be seen as getting started on that effort. axum's body types could be moved to hyper or http-body if thats the direction we decide on.
The types I'm thinking about adding are:
- `StreamBody`- added in this PR
- `AsyncReadBody` - similar to [http-body#41](https://github.com/hyperium/http-body/pull/41/files)
- `ChannelBody` - similar to `hyper::Body::channel`
Previously extractors worked directly on `Request<B>` which meant you
had to do weird tricks like `mem::take(req.headers_mut())` to get owned
parts of the request.
This changes that instead to use a new `RequestParts` type that have
methods to "take" each part of the request. Without having to do weird
tricks.
Also removed the need to have `B: Default` for body extractors.
Wrapping everything in `crate::body::Either` wasn't actually necessary
ans probably causes large body types. You can instead box the bodies in
the leaf services.
Previously, when routing between one or two requests the two body types
would be merged by boxing them. This isn't ideal since it introduces a
layer indirection for each route.
We can't require the services to be routed between as not all services
use the same body type.
This changes that so it instead uses an `Either` enum that implements
`http_body::Body` if each variant does. Will reduce the overall
allocations and hopefully the compiler can optimize things if both
variants are the same.
David Pedersen