Do not add a Content-Type header to the HTTP upgrade request (#127)

Do not add a `Content-Type` header to the HTTP upgrade request.

Fixes #126.

[Some](https://alpaca.markets/docs/api-references/trading-api/streaming/) WebSocket servers use the `Content-Type` header to determine which serialization format to use for its WebSocket messages. However, `HTTPInitialRequestHandler` [adds](https://github.com/vapor/websocket-kit/blob/62f568aa9d338aa33790534fa7b5800976f93af8/Sources/WebSocketKit/HTTPInitialRequestHandler.swift#L24) a hard-coded `Content-Type: text/plain; charset=utf-8` header to the WebSocket client’s HTTP upgrade request, so the client cannot customize the header value.

Given that the HTTP upgrade request body is empty, there is no need for `HTTPInitialRequestHandler` to add the `Content-Type` header. This will allow the client to add their own, if desired.

Co-authored-by: fumoboy007 <fumoboy007@me.com>
Co-authored-by: Tim Condon <0xTim@users.noreply.github.com>

Sources/WebSocketKit/HTTPInitialRequestHandler.swift

@@ -21,7 +21,6 @@ final class HTTPInitialRequestHandler: ChannelInboundHandler, RemovableChannelHa
 
     func channelActive(context: ChannelHandlerContext) {
         var headers = self.headers
-        headers.add(name: "Content-Type", value: "text/plain; charset=utf-8")
         headers.add(name: "Host", value: self.host)
 
         var uri = self.path.hasPrefix("/") ? self.path : "/" + self.path

Tests/WebSocketKitTests/WebSocketKitTests.swift

@@ -179,12 +179,20 @@ final class WebSocketKitTests: XCTestCase {
     func testHeadersAreSent() throws {
         let promiseAuth = self.elg.next().makePromise(of: String.self)
 
-        // make sure there is no content-length header
-        let promiseNoContentLength = self.elg.next().makePromise(of: Bool.self)
+        // make sure there are no unwanted headers such as `Content-Length` or `Content-Type`
+        let promiseHasUnwantedHeaders = self.elg.next().makePromise(of: Bool.self)
 
         let server = try ServerBootstrap.webSocket(on: self.elg) { req, ws in
-            promiseAuth.succeed(req.headers.first(name: "Auth")!)
-            promiseNoContentLength.succeed(req.headers.contains(name: "content-length"))
+            let headers = req.headers
+
+            promiseAuth.succeed(headers.first(name: "Auth")!)
+
+            let hasUnwantedHeaders = (
+                headers.contains(name: "Content-Length") ||
+                headers.contains(name: "Content-Type")
+            )
+            promiseHasUnwantedHeaders.succeed(hasUnwantedHeaders)
+
             ws.close(promise: nil)
         }.bind(host: "localhost", port: 0).wait()
 
@@ -201,7 +209,7 @@ final class WebSocketKitTests: XCTestCase {
             }.cascadeFailure(to: promiseAuth)
 
         try XCTAssertEqual(promiseAuth.futureResult.wait(), "supersecretsauce")
-        try XCTAssertFalse(promiseNoContentLength.futureResult.wait())
+        try XCTAssertFalse(promiseHasUnwantedHeaders.futureResult.wait())
         try server.close(mode: .all).wait()
     }