docs: client: clarify handshake error conditions

[WofWca]

What type of PR is this? (check all applicable)

• [ ] Refactor
• [ ] Feature
• [ ] Bug Fix
• [ ] Optimization
• [x] Documentation Update
• [ ] Go Version Update
• [ ] Dependency Update

Description

The purpose of this change is to set this behavior in stone, so that, for example, introducing "follow redirects" by default would be a breaking change. The WebSocket spec actually allows the client to follow redirects:

the server might redirect the client using a 3xx status code (but clients are not required to follow them)

I think this library should be explicit about whether it does this.

I feel like the existing "...so that callers can handle redirects, authentication, etcetera" is not worded strongly enough.

Background: I'm working on an application that makes connections to arbitrary addresses, so a target WebSocket server might be malicious. Thus I want to limit the scope of what a malicious server can do. For example, ensure that it's not gonna redirect the client to a private address, or to a DDoS target.

Related Tickets & Documents

Added/updated tests?

• [ ] Yes
• [x] No, and this is why: this is purely a documentation change
• [ ] I need help with writing tests

Run verifications and test

• [ ] make verify is passing
• [ ] make test is passing