feat: add tests for admin checks and error handling

- Introduced new tests for the `is_admin_async` function to verify correct behavior based on user roles.
- Added tests for error handling in the `error_handler` to ensure exceptions are logged and do not propagate.
- Enhanced test coverage for configuration settings by adding a test for parsing admin phone numbers from environment variables.
- Updated the `.cursorrules` file to include the use of a virtual environment for better dependency management.

tests/test_handlers_common.py

@@ -0,0 +1,52 @@
+"""Tests for duty_teller.handlers.common (is_admin_async)."""
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from duty_teller.handlers.common import is_admin_async
+
+
+@pytest.mark.asyncio
+async def test_is_admin_async_true_when_repository_returns_true():
+    """is_admin_async returns True when is_admin_for_telegram_user returns True."""
+    mock_session = MagicMock()
+    mock_scope = MagicMock()
+    mock_scope.return_value.__enter__.return_value = mock_session
+    mock_scope.return_value.__exit__.return_value = None
+
+    with patch(
+        "duty_teller.handlers.common.session_scope",
+        mock_scope,
+    ):
+        with patch(
+            "duty_teller.handlers.common.is_admin_for_telegram_user",
+            return_value=True,
+        ) as mock_is_admin:
+            result = await is_admin_async(12345)
+    assert result is True
+    mock_scope.assert_called_once()
+    mock_scope.return_value.__enter__.assert_called_once()
+    mock_is_admin.assert_called_once_with(mock_session, 12345)
+
+
+@pytest.mark.asyncio
+async def test_is_admin_async_false_when_repository_returns_false():
+    """is_admin_async returns False when is_admin_for_telegram_user returns False."""
+    mock_session = MagicMock()
+    mock_scope = MagicMock()
+    mock_scope.return_value.__enter__.return_value = mock_session
+    mock_scope.return_value.__exit__.return_value = None
+
+    with patch(
+        "duty_teller.handlers.common.session_scope",
+        mock_scope,
+    ):
+        with patch(
+            "duty_teller.handlers.common.is_admin_for_telegram_user",
+            return_value=False,
+        ) as mock_is_admin:
+            result = await is_admin_async(99999)
+    assert result is False
+    mock_scope.assert_called_once()
+    mock_is_admin.assert_called_once_with(mock_session, 99999)