When a user tried to have the following Edge Function:
```ts
export default () => fetch("https://example.vercel.sh");
```
The Edge Function were failing.
Why is that?
When `fetch` was called, an implicit `Accept-Encoding` header was added
to allow the origin to return a compressed response. Then, the origin
will set the `Content-Encoding` header in the response, to let the
client know that the body needs to be decompressed in order to be read.
That creates an issue though: `response.body` will be a
`ReadableStream<Uint8Array>`, or, a stream that contains binary data
that decodes into _the uncompressed data_ (or, plain text!).
What it means, is that `response.body` is uncompressed data, while
`response.headers.get('content-encoding')` is marking the response body
as compressed payload. This confuses the HTTP clients and makes them fail.
This commit removes the `content-encoding`, `transfer-encoding` and
`content-length` headers from the response, as the Next.js server _always_
streams Edge Function responses.
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
41d4aa04c4