feat(ws): support handleMessage option on ws.link

[kettanaito]

• Related to WebSocket Support Beta #2010, feat: support mocking WebSocket APIs #2011
• Implements WebSocket Support Beta #2010 (comment)

This pull request aims to accomplish a few things:

1. Give the developer a clear API to modify the incoming/outgoing data in the WebSocket connection.
2. Make the support for third-party bindings apply to the entire ws.link(), not individual connections (i.e. consistency).

Roadmap

• Document the ws.link options.
• Check if this API is sufficient for https://github.com/mswjs/socket.io-binding to be rewritten as a custom handleMessage function.
  • Needs binaryType (https://github.com/mswjs/socket.io-binding/blob/0db8a6193f06c2196cfd1880d07e153fa702e591/src/index.ts#L36)
  • This pull request doesn't provide any means to create custom methods on connection, like .emit() (https://github.com/mswjs/socket.io-binding/blob/0db8a6193f06c2196cfd1880d07e153fa702e591/src/index.ts#L81)
  • This API provides no access to the actual server connection (https://github.com/mswjs/socket.io-binding/blob/0db8a6193f06c2196cfd1880d07e153fa702e591/src/index.ts#L137)
  • Some clients may represent a single message as multiple messages (e.g. how socket.io handles Blobs) (https://github.com/mswjs/socket.io-binding/blob/0db8a6193f06c2196cfd1880d07e153fa702e591/src/index.ts#L107)

Given that the binding requires more functionality (to return more functionality), perhaps a binding can ship multiple things: a custom handlMessage function to encoding/decoding, and something like extend() to provide new methods on the connection (or create new properties on the connection).

With this brief analysis, it looks like a single handleMessage option won't be enough to hook in a custom binding to your WebSocket connection. I may need to explore other means to provide a consistent, connection-wide API to augment the connection.

[kettanaito]

Going to close this for now. In its current state, this is a bad proposal.