Add tracking system to support optional PostHog tracking in AI engine (#6040)

Co-authored-by: ConnorYoh <[email protected]>

engine/tests/conftest.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+from collections.abc import Iterator
+
+import pytest
+
+from stirling.config import AppSettings, load_settings
+from stirling.services import build_runtime
+from stirling.services.runtime import AppRuntime
+
+
+@pytest.fixture(autouse=True)
+def clear_settings_cache() -> Iterator[None]:
+    load_settings.cache_clear()
+    yield
+    load_settings.cache_clear()
+
+
+def build_app_settings() -> AppSettings:
+    return AppSettings(
+        smart_model_name="test",
+        fast_model_name="test",
+        smart_model_max_tokens=8192,
+        fast_model_max_tokens=2048,
+        posthog_enabled=False,
+        posthog_api_key="",
+        posthog_host="https://eu.i.posthog.com",
+    )
+
+
+@pytest.fixture
+def app_settings() -> AppSettings:
+    return build_app_settings()
+
+
+@pytest.fixture
+def runtime(app_settings: AppSettings) -> AppRuntime:
+    return build_runtime(app_settings)