WebSocket: Router doesn't parse accents from co-processor's context when connecting to subgraph

[reggermont]

Describe the bug

Hello ! I have a very specific case that triggers an unexpected error where characters with accent are badly converted:

"message": "HTTP fetch failed from 'module-test': Websocket fetch failed from 'module-test': cannot connect websocket to subgraph: invalid UTF-8 in WebSocket handshake: failed to convert header to a str for header name 'myAccent' with value: \"\\xc3\\xa8\"",

The character è should be a valid UTF-8 character: https://unicodeplus.com/U+00E8

It works well on Query / Mutation (http), but not on Subscription (ws)

To Reproduce

Steps to reproduce the behavior:

1. In co-processor, return a string with an accent in res.json

res.json({
  context: {
    entries: {
      willTriggerAnError: "è",
    },
  },
});

2. Configure router to insert header from context

headers:
  all:
    request:
      - insert:
          name: myAccent
          from_context: willTriggerAnError

3. See error

Expected behavior

No error