This commit involves several breaking changes:
* `session_key` config param must be a 256-bit base64 encoded string.
* `FromRequest` is implemented for `Cookies`, not `Cookie`.
* Only a single `Cookies` instance can be retrieved at a time.
* `Config::take_session_key` returns a `Vec<u8>`.
* `Into<Header>` is implemented for `&Cookie`, not `Cookie`.
A few interesting notes on this breakage:
* `Cookie` how has a lifetime. It should be `'static'` everywhere.
* The `SetCookie` header is no longer reexported.
* Instead, `Cookie` implements `Into<Header>` for Set-Cookie.
This is a complete rework of `Responder`s and of the http backend in
general. This gets Rocket one step closer to HTTP library independence,
enabling many future features such as transparent async I/O, automatic
HEAD request parsing, pre/post hooks, and more.
Summary of changes:
* `Responder::response` no longer takes in `FreshHyperResponse`.
Instead, it returns a new `Response` type.
* The new `Response` type now encapsulates a full HTTP response. As a
result, `Responder`s now return it.
* The `Handler` type now returns an `Outcome` directly.
* The `ErrorHandler` returns a `Result`. It can no longer forward,
which made no sense previously.
* `Stream` accepts a chunked size parameter.
* `StatusCode` removed in favor of new `Status` type.
* `ContentType` significantly modified.
* New, lightweight `Header` type that plays nicely with `Response`.
Sergio Benitez