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
The `Set-Cookie` header is an exceptional case where multiple values are allowed, and should not be joined into a single header. Because of its browser-focussed origins (where set-cookie is not visible), `fetch()` does not have a clean API for this. Instead we have to access the `raw()` data.
This fixes various authentication-related issues when developing via the Ember CLI proxy.
node-fetch is now a ES module, so it has to either imported with `import/from` syntax (which can't be used in addon's index.js) or using the dynamic `import()`
