Implement publishing and joining worlds

[lactyy]

Adds a support for publishing and joining worlds displayed in the friend list. Closes #219.

WIP. I might separate these packages into a different module to reduce usage of huge dependencies added for WebRTC.

Task Lists:

• Implement listening on NetherNet
• Implement publishing worlds
• Implement dialing on NetherNet
• Implement looking up worlds
• Properly write a documentation on types, methods, fields, etc. (Help needed...)
• Implement LAN discovery

[lactyy]

The changes in pull request and other packages, which have been split into separate modules, has been fully documented.

[HashimTheArab]

the comment says this method is blocking but the select has a default case

[HashimTheArab]

dont forget to change this to a string

[HashimTheArab]

actually its sent as either a string UUID or a uint64, not a string-based uint64 so this needs a custom type which supports string | uint64 decoding

[HashimTheArab]

would change this to func (status Status) NetherNetID()

[HashimTheArab]

this should check x.Valid() but the whole function can be improved like this

func (r *refreshTokenSource) Token() (_ xsapi.Token, err error) {
	r.mu.Lock()
	defer r.mu.Unlock()

	// Return the cached XBL token if it is valid.
	if r.x != nil && r.x.Valid() {
		return r.x, nil
	}

	// Request a new underlying token if it is not valid.
	if r.t == nil || !r.t.Valid() {
		r.t, err = r.underlying.Token()
		if err != nil {
			return nil, fmt.Errorf("request underlying token: %w", err)
		}
	}

	// Request a new XBL token using the underlying token.
	r.x, err = auth.RequestXBLToken(r.ctx, r.t, r.relyingParty)
	if err != nil {
		return nil, fmt.Errorf("request xbox live token: %w", err)
	}

	return r.x, nil
}

[Sandertv]

What needs to be done to get this updated to use the new auth that was merged?

[lactyy]

First, we need an implementation for connecting to the signaling service provided by Minecraft.

At the moment, Minecraft uses two different signaling methods:

• JSON-over-WebSocket
• JSONRPC-over-WebSocket (referred to as Player Messaging), which is being gradually rolled out to users depending on treatment contexts.

On top of that, we need support for announcing, discovering, and joining worlds via Xbox Live, with compatibility for both signaling methods mentioned above.

Finally, on the protocol, we need:

• support for custom batch headers in packets (for example, 0xfe is used by RakNet, but this is not present in NetherNet packets), and
• a way to disable encryption in packet.Encoder and packet.Decoder.

[lactyy]

I’m currently rewriting df-mc/go-xsapi to make it more usable for this PR, and it includes a new implementation for Xbox Live authentication.

During this work, I found that the relying party for XBL tokens can be determined automatically based on the request URL, so my fork includes support for that as well.

I’m planning to submit a PR to df-mc/go-xsapi, but it isn’t ready yet.