feat!: report the package proxy as a fact; no warnings of its own (0.9.0)

get_device_warnings decided two things for the application: that any
pending update is a warning (it re-read the updates for that), and
whether apt's proxy is the one the application's setting wants, which
it was handed as optional_args["apt_proxy_url"].

The driver reports facts instead (napalm-device-types 4.14):
get_package_proxy() says which proxy apt fetches through, None for none
or on a non-apt host; the updates are get_available_updates() as
before. get_device_warnings and the apt_proxy_url argument go.

BREAKING CHANGE: get_device_warnings and optional_args["apt_proxy_url"]
are removed. Requires napalm-device-types 4.14.

Closes #28

napalm_linux/linux.py

@@ -346,8 +346,6 @@ class LinuxDriver(
         # Optional sudo password for privilege escalation (e.g. apt-get update)
         self._sudo_password: str | None = optional_args.get("sudo_password")
         # Expected apt proxy URL — checked as a device warning on apt systems.
-        # Only set when apt_proxy_enabled=true in NetOrk settings; empty string disables the check.
-        self._apt_proxy_url: str = optional_args.get("apt_proxy_url", "")
 
         if optional_args.get("debugging"):
             logger.setLevel(logging.DEBUG)
@@ -1510,38 +1508,13 @@ class LinuxDriver(
             f"Package manager '{self._pkg_manager}' is not supported"
         )
 
-    def get_device_warnings(self) -> List[dict[str, Any]]:
-        """Return warning dicts for issues detected on this device.
-
-        Currently detects:
-        - package updates available (uses local package cache)
-        - apt proxy not configured (apt systems only)
-        """
-        warnings: List[dict[str, Any]] = []
-        try:
-            updates = self.get_available_updates()
-        except Exception as exc:
-            logger.warning("get_device_warnings: get_available_updates() failed: %s", exc)
-            updates = []
-        if updates:
-            warnings.append({
-                "code": "updates_available",
-                "meta": {
-                    "count": len(updates),
-                    "packages": [u.get("name", "") for u in updates],
-                },
-            })
-        if self._pkg_manager == "apt" and self._apt_proxy_url:
-            try:
-                current = self._send("cat /etc/apt/apt.conf.d/00proxy 2>/dev/null || true").strip()
-                if self._apt_proxy_url not in current:
-                    warnings.append({
-                        "code": "apt_proxy_missing",
-                        "meta": {"expected_url": self._apt_proxy_url},
-                    })
-            except Exception as exc:
-                logger.warning("get_device_warnings: apt proxy check failed: %s", exc)
-        return warnings
+    def get_package_proxy(self) -> str | None:
+        """The proxy apt fetches through (``00proxy``); None for none or a non-apt host."""
+        if self._pkg_manager != "apt":
+            return None
+        conf = self._send(f"cat {_APT_PROXY_CONF} 2>/dev/null || true")
+        found = re.search(r'Acquire::http::Proxy\s+"([^"]+)"', conf)
+        return found.group(1) if found else None
 
     def _get_updates_apt(self) -> list[UpdateDict]:
         # apt list --upgradable does not need root; avoid sudo so it works even