fix #300 DHCPv6 over A10NSP

[GIC-de]

This merge request addresses the DHCPv6 A10NSP server behavior by ensuring that the interface-id option from the relay-forward message is copied to the relay-reply message.

Additionally, it includes fixes to properly parse and display the agent-circuit-id (interface-id) and agent-remote-id (remote-id) learned from the relay-forward message, enabling testing of intermediate LDRA agents.

$ sudo bngblaster-cli run.sock session-info session-id 1
{
    "status": "ok",
    "code": 200,
    "session-info": {
        "type": "ipoe",
        "session-id": 1,
        "session-state": "Established",
        "session-version": 4,
        "flapped": 0,
        "interface": "veth1.2",
        "outer-vlan": 1,
        "inner-vlan": 7,
        "mac": "02:00:00:00:00:01",
        "agent-circuit-id": "0.0.0.0/0.0.0.0 eth 1:7",
        "agent-remote-id": "DEU.RTBRICK.1",
...
        "a10nsp": {
            "interface": "veth1.1",
            "s-vlan": 1,
            "qinq-send": false,
            "qinq-received": false,
            "dhcp-aci": "0.0.0.0/0.0.0.0 eth 1:7",
            "dhcp-ari": "DEU.RTBRICK.1",
            "dhcpv6-aci": "0.0.0.0/0.0.0.0 eth 1:7", <<<<<<<<<<<<<<<
            "dhcpv6-ari": "DEU.RTBRICK.1", <<<<<<<<<<<<<<<
            "tx-packets": 5,
            "rx-packets": 5
        }
    }
}