Use ResponseBody closure to write response

FIx tests, up the hummingbird version

response-body-processing/Package.swift

@@ -10,7 +10,7 @@ let package = Package(
         .executable(name: "App", targets: ["App"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/hummingbird-project/hummingbird.git", from: "2.0.0-rc.1"),
+        .package(url: "https://github.com/hummingbird-project/hummingbird.git", from: "2.0.0-rc.4"),
         .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.3.0"),
         .package(url: "https://github.com/apple/swift-crypto", from: "3.0.0"),
     ],

response-body-processing/Sources/App/Application+build.swift

@@ -28,10 +28,16 @@ public func buildApplication(_ arguments: some AppArguments) async throws -> som
     router.add(middleware: AddSHA256DigestMiddleware())
     // Add echo route
     router.post("/echo") { request, context -> Response in
+        // Demostrating returning a ResponseBody initialized with a closure writing the contents
+        // of the body. This is the equivalent of `ResponseBody(asyncSequence: request.body)``
+        let responseBody = ResponseBody { writer in
+            try await writer.write(request.body)
+            try await writer.finish(nil)
+        }
         return Response(
             status: .ok,
             headers: [.contentType: request.headers[.contentType] ?? "application/octet-stream"],
-            body: .init(asyncSequence: request.body)
+            body: responseBody
         )
     }
     let app = Application(

response-body-processing/Tests/AppTests/AppTests.swift

@@ -25,7 +25,7 @@ final class AppTests: XCTestCase {
         let buffer = Self.randomBuffer(size: 256 * 000)
         let digest = SHA256.hash(data: Data(buffer.readableBytesView))
         try await app.test(.live) { client in
-            try await client.execute(uri: "/echo", method: .get, body: buffer) { response in
+            try await client.execute(uri: "/echo", method: .post, body: buffer) { response in
                 XCTAssertEqual(
                     response.trailerHeaders?[.digest],
                     "sha256=\(digest.hexDigest())"