middleware: Implement proxy URI paths to RPC methods (#859)
* middleware: Proxy `GET /path` requests to internal methods Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Modify the response for proxies Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * examples: Add `ProxyRequestLayer` example for URI redirection Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * http: Remove internal Health API Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Replace `ResponseFuture` with pinning Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Use `Uri::from_static` and `RequestSer` for body message Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Use `Arc<str>` instead of `String` Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Rename `ProxyRequest` to `ProxyGetRequest` and rename mod to `middleware` Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Improve docs Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * middleware: Fail if path does not start with `/` Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * http-server: Remove pin project dependency Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Rename `proxy_request.rs` to `proxy_get_request.rs` Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>