feat!: report the subscription as a license, not a warning (0.4.0)

get_device_warnings is gone; netOrk names the warnings from facts
(netOrk #1111). lldpd and the pending updates were already facts
(get_packages, get_available_updates). The subscription is now
get_licenses() from napalm-device-types 4.14's LicenseMixin: one
pve-subscription entry, the API status mapped to a LicenseStatus.

The old check compared against "NotFound" while the API answers
"notfound" (seen on all four nodes), so it never fired; the mapping is
case-insensitive.

tests/test_licenses.py

@@ -0,0 +1,62 @@
+"""The node's subscription as a fact (netOrk #1111).
+
+The driver named ``no_subscription`` itself, comparing against "NotFound" while
+the API answers "notfound" -- so it never fired. It reports the subscription
+now; whether a missing one is a warning is the caller's decision.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from napalm_proxmox import ProxmoxDriver
+
+
+def _driver(subscription: dict) -> ProxmoxDriver:
+    d = ProxmoxDriver("pve", "root@pam", "pw")
+    d._get_node_subscription = lambda: subscription
+    return d
+
+
+@pytest.mark.parametrize(
+    "raw, status",
+    [
+        ("notfound", "none"),
+        ("NotFound", "none"),
+        ("active", "active"),
+        ("invalid", "invalid"),
+        ("expired", "expired"),
+        ("new", "unknown"),
+        ("suspended", "unknown"),
+    ],
+)
+def test_the_api_status_as_a_license_status(raw, status):
+    [lic] = _driver({"status": raw, "message": "There is no subscription key"}).get_licenses()
+
+    assert lic["name"] == "pve-subscription"
+    assert lic["status"] == status
+    assert lic["detail"] == "There is no subscription key"
+
+
+def test_level_and_due_date_when_subscribed():
+    sub = {
+        "status": "active",
+        "productname": "Proxmox VE Community Subscription 1 CPU/year",
+        "nextduedate": "2027-03-01",
+    }
+    [lic] = _driver(sub).get_licenses()
+
+    assert lic["edition"] == "Proxmox VE Community Subscription 1 CPU/year"
+    assert lic["expires"] == "2027-03-01"
+
+
+def test_an_unreadable_subscription_reports_nothing():
+    """``_get_node_subscription`` gives {} when the API call fails: no fact, not "none"."""
+    assert _driver({}).get_licenses() == []
+
+
+def test_no_warnings_of_its_own():
+    """lldpd, the updates and the subscription are facts the caller reads
+    (get_packages, get_available_updates, get_licenses)."""
+    assert not any("get_device_warnings" in vars(c) for c in ProxmoxDriver.__mro__[:-1]
+                   if c.__module__.startswith("napalm_proxmox"))