refactor: WireGuard tunnels are read in their own module (#32)

get_vpn_tunnels() grew past the quality baseline with the key fix. The
WireGuard part is pure parsing of /api/wireguard/service/show, like the
listen ports in listening.py, so it moves to wireguard.py and the driver
calls it. opnsense.py shrinks from 3125 to 3082 lines.

napalm_opnsense/wireguard.py

@@ -0,0 +1,73 @@
+"""WireGuard peers as VPN tunnels. Pure: no I/O.
+
+``/api/wireguard/service/show`` lists every WireGuard interface and peer::
+
+    {"total": N, "rows": [
+      {"if": "wg0", "type": "interface", ...},
+      {"if": "wg0", "type": "peer", "public-key": "...",
+       "endpoint": "1.2.3.4:51820", "transfer-rx": N, "transfer-tx": N,
+       "name": "office", "peer-status": "online",
+       "latest-handshake-age": 45, "ifname": "office"}, ...
+    ]}
+
+**The key is the peer, not its place.** It used to be a running counter, so a
+peer added ahead of another renumbered it, and whatever a consumer keeps per
+key (netOrk's site link, its tunnel check) moved to a different peer (#32).
+Now it is the interface and the start of the public key, as napalm-linux does
+it, with the base64 made URL-safe because the key is used as a path segment.
+Two peers sharing the prefix get the whole key; a row without a public key
+keeps its position.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+#: How much of a public key names a peer, the same length as napalm-linux uses.
+_KEY_PREFIX = 8
+
+
+def _key(row: dict[str, Any], position: int, taken: dict[str, Any]) -> str:
+    public_key = (row.get("public-key") or "").strip()
+    if not public_key:
+        return f"wireguard-{position}"
+    safe = public_key.rstrip("=").replace("+", "-").replace("/", "_")
+    key = f"wireguard-{row.get('if') or 'wg'}-{safe[:_KEY_PREFIX]}"
+    if key in taken:
+        key = f"wireguard-{row.get('if') or 'wg'}-{safe}"
+    return key
+
+
+def _remote_ip(row: dict[str, Any]) -> str:
+    endpoint = (row.get("endpoint") or "").strip()
+    if not endpoint or endpoint == "(none)":
+        return ""
+    return endpoint.rsplit(":", 1)[0].strip("[]")
+
+
+def _tunnel(row: dict[str, Any], position: int) -> dict[str, Any]:
+    handshake_age = row.get("latest-handshake-age")
+    return {
+        "type": "WireGuard",
+        "local_endpoint": "",
+        "remote_endpoint": _remote_ip(row),
+        "is_up": row.get("peer-status") == "online",
+        "uptime": int(handshake_age) if handshake_age else 0,
+        "bytes_in": int(row.get("transfer-rx") or 0),
+        "bytes_out": int(row.get("transfer-tx") or 0),
+        "description": (
+            (row.get("name") or "").strip()
+            or (row.get("ifname") or "").strip()
+            or f"wg-peer-{position}"
+        ),
+    }
+
+
+def wireguard_tunnels(show: Any) -> dict[str, dict[str, Any]]:
+    """One ``VPNTunnelDict`` per peer in ``/api/wireguard/service/show``, by tunnel key."""
+    rows = show.get("rows", []) if isinstance(show, dict) else []
+    tunnels: dict[str, dict[str, Any]] = {}
+    peers = [row for row in rows if isinstance(row, dict) and row.get("type") == "peer"]
+    for position, row in enumerate(peers, start=1):
+        tunnels[_key(row, position, tunnels)] = _tunnel(row, position)
+    return tunnels