Add connection identifier to log lines for multi-client applications

[Copilot]

Problem

When running multiple AMQP clients in a single application, it was impossible to distinguish which log lines belonged to which connection. This made debugging and monitoring difficult in production environments with multiple concurrent connections.

Solution

Added a unique connection identifier to all log lines using Crystal's Log.context feature. The identifier is:

• For TCP/SSL connections: The local port number (e.g., 54321)
• For UNIX sockets/WebSockets: The object ID

Using the local port number (as suggested in #issue-comment) provides an excellent identifier because:

• It's unique per TCP connection on the host
• Easy to correlate with network debugging tools (tcpdump, netstat, etc.)
• Visible in server logs and management interfaces
• Requires no additional configuration

Implementation Details

The connection identifier is:

1. Extracted during connection initialization from the socket's local address
2. Stored in the @connection_id instance variable
3. Set in the log context for all logging operations:
   • Incoming frame processing (read_loop)
   • Outgoing frame writing (unsafe_write)
   • Connection lifecycle events (close)

Example Output

Before:

DEBUG - recv Frame::Basic::Deliver(...)
DEBUG - sent Frame::Basic::Ack(...)

After (with two connections):

DEBUG - recv Frame::Basic::Deliver(...) connection_id=54321
DEBUG - sent Frame::Basic::Ack(...) connection_id=54321
DEBUG - recv Frame::Basic::Deliver(...) connection_id=54322
DEBUG - sent Frame::Basic::Ack(...) connection_id=54322

Testing

• Added unit test to verify @connection_id is properly set
• Created example script (examples/connection_identifier_test.cr) demonstrating the feature with multiple connections
• All existing tests continue to pass

Fixes #[issue-number]

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add some kind of identifier to log lines</issue_title>
<issue_description>If you have multiple amqp-clients in one application you can't tell which logs belong to which clients. It would be good with some kind of identifier that follows one client's log. Maybe just the #object_id for the Connection.</issue_description>

Comments on the Issue (you are @copilot in this section)

@carlhoerberg Src port should be unique between client connections?

Fixes #62

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[carlhoerberg]

A but superfluous?

[carlhoerberg]

I guess this makes sense in LavinMQ, but from a clients perspective, remote_address.to_s would make more sense. Maybe users should be over to override it?

Suggested change

	io.local_address.port.to_s
	io.remote_address.to_s

[carlhoerberg]

this sets the metadata for the rest of the calling fiber's lifetime. You probably want to use Log.with_context(b: 2) do, that resets the metadata after the block