feat(interfaces): report the assigned interface name alongside the physical one

get_interfaces() keys entries by the physical device ("em0"), which is what
every other call in this driver speaks. Wake-on-LAN is the exception: it needs
the name OPNsense assigned ("lan", "opt1") and silently rejects anything else
with an empty {} at HTTP 200.

The overview export already carries it, so pass it through as "identifier".
Empty for interfaces OPNsense has not assigned.

napalm_opnsense/opnsense.py

@@ -220,6 +220,11 @@ class OPNsenseDriver(OPNsensePingMixin, FirewallDriver):
         Each entry contains NAPALM standard keys:
         ``is_up``, ``is_enabled``, ``description``, ``last_flapped``,
         ``mac_address``, ``speed``, ``mtu``.
+
+        Plus one non-standard key, ``identifier``: OPNsense's *assigned*
+        interface name ("lan", "opt1"), as opposed to the physical device the
+        dict is keyed by ("em0"). Empty for unassigned interfaces. This is the
+        name :meth:`send_wake_on_lan` requires — see the note there.
         """
         data = self._get("/api/interfaces/overview/export")
         interfaces: dict[str, dict[str, Any]] = {}
@@ -240,6 +245,7 @@ class OPNsenseDriver(OPNsensePingMixin, FirewallDriver):
                 "mac_address": (iface.get("macaddr") or iface.get("mac") or "").lower(),
                 "speed": float(iface["speed_mbps"]) if iface.get("speed_mbps") else 0.0,
                 "mtu": int(iface["mtu"]) if iface.get("mtu") else 0,
+                "identifier": iface.get("identifier") or "",
             }
 
         return interfaces