Security: Replace urllib.request with httpx in WebDAV testing

The `_test_webdav_connection` function previously used `urllib.request.urlopen`
to verify connection credentials. This triggers a Bandit B310 warning because
`urllib` supports multiple schemes (like file://, ftp://) and implicitly follows
redirects.

Although scheme checking and a basic `is_private_ip` validation were implemented,
using `urllib.request` remains risky because a public URL could return an
HTTP redirect to a private IP (e.g., 127.0.0.1) which `urllib` would blindly follow,
causing an SSRF (Server-Side Request Forgery) bypass.

This commit replaces `urllib.request` with `httpx.request` using explicitly
`follow_redirects=False`. This eliminates the B310 vulnerability, ensures
requests only hit the specified URL without following potentially malicious
redirects, and standardizes the application on `httpx` for safer HTTP connections.

In addition to fixing the vulnerability, test coverage is added for the
new WebDAV connections logic.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_api_integrations.py

@@ -1,5 +1,6 @@
 """Tests for the per-user integrations API (app/api/integrations.py)."""
 
+import unittest.mock
 import pytest
 from fastapi.testclient import TestClient
 from sqlalchemy import create_engine
@@ -1061,6 +1062,69 @@ class TestConnectionTestEndpoint:
         assert data["success"] is False
         assert "scheme" in data["message"].lower()
 
+    @unittest.mock.patch("httpx.request")
+    def test_test_webdav_success(self, mock_request, int_client):
+        """WebDAV test succeeds with valid credentials and a valid status code."""
+        mock_response = unittest.mock.MagicMock()
+        mock_response.status_code = 207  # Typical WebDAV success for PROPFIND
+        mock_request.return_value = mock_response
+
+        payload = {
+            "integration_type": "WEBDAV",
+            "config": {"url": "https://example.com/webdav"},
+            "credentials": {"username": "user1", "password": "password123"},
+        }
+        resp = int_client.post("/api/integrations/test", json=payload)
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is True
+
+        mock_request.assert_called_once_with(
+            "PROPFIND",
+            "https://example.com/webdav",
+            auth=("user1", "password123"),
+            headers={"Depth": "0"},
+            timeout=10.0,
+            follow_redirects=False,
+        )
+
+    @unittest.mock.patch("httpx.request")
+    def test_test_webdav_failure_status(self, mock_request, int_client):
+        """WebDAV test fails if the server returns a 4xx or 5xx status code."""
+        mock_response = unittest.mock.MagicMock()
+        mock_response.status_code = 401
+        mock_request.return_value = mock_response
+
+        payload = {
+            "integration_type": "WEBDAV",
+            "config": {"url": "https://example.com/webdav"},
+            "credentials": {"username": "user1", "password": "wrong"},
+        }
+        resp = int_client.post("/api/integrations/test", json=payload)
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is False
+        assert "401" in data["message"]
+
+    @unittest.mock.patch("httpx.request")
+    def test_test_webdav_exception(self, mock_request, int_client):
+        """WebDAV test fails gracefully if an exception occurs during the request."""
+        mock_request.side_effect = Exception("Connection error")
+
+        payload = {
+            "integration_type": "WEBDAV",
+            "config": {"url": "https://example.com/webdav"},
+            "credentials": {},
+        }
+        resp = int_client.post("/api/integrations/test", json=payload)
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is False
+        assert "failed" in data["message"].lower()
+
 
 # ---------------------------------------------------------------------------
 # Quota endpoint tests