feat: implement cmd/relay

[emlautarom1]

Closes #182

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There is an ignored test due to a missing feature in the Relay (/metrics endpoint). We'll revisit this later when we pick up this feature again.

[Copilot]

Pull request overview

This PR implements the cmd/relay functionality by porting the relay command from the reference Go implementation. The relay server enables libp2p circuit relay functionality that allows Charon clients to discover and connect to their peers.

Changes:

• Adds new relay command to CLI with comprehensive configuration options for P2P, logging, and monitoring
• Implements relay server with QUIC support in addition to TCP
• Adds graceful shutdown handling via Ctrl+C signal
• Includes comprehensive test suite (one test ignored pending /metrics endpoint implementation)

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/relay-server/src/p2p.rs	Updates to use new multiaddr methods from P2P config for TCP/UDP listening
crates/relay-server/src/error.rs	Adds P2PConfigError variant for improved error handling
crates/relay-server/src/config.rs	Changes data_dir from Option to PathBuf with default value ".charon"
crates/p2p/src/p2p.rs	Adds QUIC support to relay server and removes unnecessary keypair clone
crates/cli/src/main.rs	Implements top-level Ctrl+C handling and adds relay command route
crates/cli/src/error.rs	Changes CliError visibility to public and adds error variants
crates/cli/src/commands/relay.rs	New 558-line implementation of relay command with args, config conversion, and tests
crates/cli/src/commands/mod.rs	Exports new relay module
crates/cli/src/cli.rs	Adds Relay command variant to CLI structure
crates/cli/Cargo.toml	Adds relay-server, tracing, libp2p, and backon dependencies
Cargo.toml	Removes unused eth2_keystore optimization
Cargo.lock	Updates dependencies including alloy, futures, and other transitive deps

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[varex83]

Small non-blocking comments, everything else looks great! LGTM!

[varex83]

Also one note - while testing it locally I had to run cargo update to fix the dependecy problems with alloy

[emlautarom1]

Also one note - while testing it locally I had to run cargo update to fix the dependecy problems with alloy

What problem did you find? CI did not show any issues on either platform.

[varex83]

What problem did you find? CI did not show any issues on either platform.

It was related that the latest alloy version is not supported by the rust version we use (1.89) and it required something like 1.91/1.92

[emlautarom1]

This check was incorrect:

Go considers :1234 a valid TCP address with a nil IP, thus it was rejected with an error: https://github.com/ObolNetwork/charon/blob/749d2d7ab0b8ace34f2e686a5af5910c8adb4dc0/p2p/config.go#L103-L114

In Rust this string results in a parse error. Our check for is_unspecified() then was incorrect since it would reject 0.0.0.0 as address while the Go code does not.

To verify, I've ran the following test in Go and added its equivalent in Rust:

func TestResolveListenAddrAllInterfaces(t *testing.T) {
	c := Config{
		TCPAddrs: []string{
			"0.0.0.0:0",
		},
		UDPAddrs: []string{
			"0.0.0.0:0",
		},
	}
	_, err := c.TCPMultiaddrs()
	require.NoError(t, err)

	_, err = c.UDPMultiaddrs()
	require.NoError(t, err)
}