DEV: Use message-bus chunked encoding in development (#19878)

This was previously disabled because of incompatibility with the ember-cli proxy. This commit fixes that incompatibility, and restores the development behaviour to match production.

There were three issues at play:

1. Our bootstrap-js addon handles the forwarding of most requests in the ember-cli proxy. This is not built to handle streaming responses. Solution: skip our custom request processing for `/message-bus/*` and use ember-cli's default `http-proxy`.

2. The request/response size-limiting middleware (`rawMiddleware`) would apply even to unhandled paths, causing request and response bodies to be buffered. Solution: skip it for any paths which are not handled by our custom addon.

3. Expressjs servers will buffer/compress responses. Solution: add `Cache-Control: no-transform` to message-bus responses. For now I've done this in development only, but it may be useful to add it to message-bus's default headers in future

app/assets/javascripts/bootstrap-json/index.js

@@ -463,6 +463,13 @@ to serve API requests. For example:
     baseURL = rootURL === "" ? "/" : cleanBaseURL(rootURL || baseURL);
 
     const rawMiddleware = express.raw({ type: () => true, limit: "100mb" });
+    const pathRestrictedRawMiddleware = (req, res, next) => {
+      if (this.shouldHandleRequest(req, baseURL)) {
+        return rawMiddleware(req, res, next);
+      } else {
+        return next();
+      }
+    };
 
     app.use(
       "/favicon.ico",
@@ -474,9 +481,9 @@ to serve API requests. For example:
       )
     );
 
-    app.use(rawMiddleware, async (req, res, next) => {
+    app.use(pathRestrictedRawMiddleware, async (req, res, next) => {
       try {
-        if (this.shouldForwardRequest(req, baseURL)) {
+        if (this.shouldHandleRequest(req, baseURL)) {
           await handleRequest(proxy, baseURL, req, res);
         } else {
           // Fixes issues when using e.g. "localhost" instead of loopback IP address
@@ -497,7 +504,7 @@ to serve API requests. For example:
     });
   },
 
-  shouldForwardRequest(request, baseURL) {
+  shouldHandleRequest(request, baseURL) {
     if (
       [
         `${baseURL}tests/index.html`,
@@ -513,6 +520,10 @@ to serve API requests. For example:
       return false;
     }
 
+    if (request.path.startsWith(`${baseURL}message-bus/`)) {
+      return false;
+    }
+
     return true;
   },
 };