📈(backend) introduce analytics

In this commit, we'll integrate a third-party service to track user events.
We start by using the `identify` method to track sign-ins and sign-ups.

Additionally, we use the `track` method to monitor custom events such as room
creation, access token generation, and logouts. This will provide us with
valuable data on current usage patterns.

The analytics library operates by opening a queue in a separate thread for
posting events, ensuring it remains non-blocking for the API. Let's test
this in a real-world scenario.

src/backend/core/tests/test_analytics.py

@@ -0,0 +1,132 @@
+"""
+Test for the Analytics class.
+"""
+
+# pylint: disable=W0212
+
+from unittest.mock import patch
+
+from django.contrib.auth.models import AnonymousUser
+from django.test.utils import override_settings
+
+import pytest
+
+from core.analytics import Analytics
+from core.factories import UserFactory
+
+pytestmark = pytest.mark.django_db
+
+
+@pytest.fixture(name="mock_june_analytics")
+def _mock_june_analytics():
+    with patch("core.analytics.jAnalytics") as mock:
+        yield mock
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_init_enabled(mock_june_analytics):
+    """Should enable analytics and set the write key correctly when ANALYTICS_KEY is set."""
+    analytics = Analytics()
+    assert analytics._enabled is True
+    assert mock_june_analytics.write_key == "test_key"
+
+
+@override_settings(ANALYTICS_KEY=None)
+def test_analytics_init_disabled():
+    """Should disable analytics when ANALYTICS_KEY is not set."""
+    analytics = Analytics()
+    assert analytics._enabled is False
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_identify_user(mock_june_analytics):
+    """Should identify a user with the correct traits when analytics is enabled."""
+    user = UserFactory(sub="12345", email="user@example.com")
+    analytics = Analytics()
+    analytics.identify(user)
+    mock_june_analytics.identify.assert_called_once_with(
+        user_id="12345", traits={"email": "***@example.com"}
+    )
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_identify_user_with_traits(mock_june_analytics):
+    """Should identify a user with additional traits when analytics is enabled."""
+    user = UserFactory(sub="12345", email="user@example.com")
+    analytics = Analytics()
+    analytics.identify(user, traits={"email": "user@example.com", "foo": "foo"})
+    mock_june_analytics.identify.assert_called_once_with(
+        user_id="12345", traits={"email": "***@example.com", "foo": "foo"}
+    )
+
+
+@override_settings(ANALYTICS_KEY=None)
+def test_analytics_identify_not_enabled(mock_june_analytics):
+    """Should not call identify when analytics is not enabled."""
+    user = UserFactory(sub="12345", email="user@example.com")
+    analytics = Analytics()
+    analytics.identify(user)
+    mock_june_analytics.identify.assert_not_called()
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_identify_no_user(mock_june_analytics):
+    """Should not call identify when the user is None."""
+    analytics = Analytics()
+    analytics.identify(None)
+    mock_june_analytics.identify.assert_not_called()
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_identify_anonymous_user(mock_june_analytics):
+    """Should not call identify when the user is anonymous."""
+    user = AnonymousUser()
+    analytics = Analytics()
+    analytics.identify(user)
+    mock_june_analytics.identify.assert_not_called()
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+def test_analytics_track_event(mock_june_analytics):
+    """Should track an event with the correct user and event details when analytics is enabled."""
+    user = UserFactory(sub="12345")
+    analytics = Analytics()
+    analytics.track(user, event="test_event", foo="foo")
+    mock_june_analytics.track.assert_called_once_with(
+        user_id="12345", event="test_event", foo="foo"
+    )
+
+
+@override_settings(ANALYTICS_KEY=None)
+def test_analytics_track_event_not_enabled(mock_june_analytics):
+    """Should not call track when analytics is not enabled."""
+    user = UserFactory(sub="12345")
+    analytics = Analytics()
+    analytics.track(user, event="test_event", foo="foo")
+
+    mock_june_analytics.track.assert_not_called()
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+@patch("uuid.uuid4", return_value="test_uuid4")
+def test_analytics_track_event_no_user(mock_uuid4, mock_june_analytics):
+    """Should track an event with a random anonymous user ID when the user is None."""
+    analytics = Analytics()
+    analytics.track(None, event="test_event", foo="foo")
+    mock_june_analytics.track.assert_called_once_with(
+        anonymous_id="test_uuid4", event="test_event", foo="foo"
+    )
+    mock_uuid4.assert_called_once()
+
+
+@override_settings(ANALYTICS_KEY="test_key")
+@patch("uuid.uuid4", return_value="test_uuid4")
+def test_analytics_track_event_anonymous_user(mock_uuid4, mock_june_analytics):
+    """Should track an event with a random anonymous user ID when the user is anonymous."""
+    user = AnonymousUser()
+    analytics = Analytics()
+    analytics.track(user, event="test_event", foo="foo")
+    mock_june_analytics.track.assert_called_once_with(
+        anonymous_id="test_uuid4", event="test_event", foo="foo"
+    )
+    mock_uuid4.assert_called_once()