✨(backend) extend analytics module to support feature flags

Extend the AnalyticsBackend class to support
user feature flags, without a breaking change to the
current implementation.

A flag value is considered to be a bool or a string.

src/backend/core/analytics/__init__.py

@@ -19,6 +19,7 @@ from django.utils.module_loading import import_string
 
 from .base import AnalyticsBackend, NoOpAnalytics
 from .events import AnalyticsEvent
+from .user_feature_flags import UserFeatureFlag
 
 __all__ = [
     "get_analytics",
@@ -26,6 +27,8 @@ __all__ = [
     "capture",
     "AnalyticsBackend",
     "AnalyticsEvent",
+    "is_user_feature_flag_enabled",
+    "UserFeatureFlag",
 ]
 
 
@@ -57,3 +60,8 @@ def capture(
 ) -> None:
     """Record an event performed by an identified user."""
     analytics_instance.capture(user, event, properties)
+
+
+def is_user_feature_flag_enabled(user, feature_name: UserFeatureFlag) -> bool:
+    """Check if a feature is enabled at the user level."""
+    return analytics_instance.is_user_feature_enabled(user, feature_name)

src/backend/core/analytics/base.py

@@ -1,10 +1,11 @@
 """Analytics backend protocol and default no-op implementation."""
 
 from abc import ABC, abstractmethod
-from typing import Any
+from typing import Any, Mapping
 
 from ..models import User
 from .events import AnalyticsEvent
+from .user_feature_flags import UserFeatureFlag
 
 
 class AnalyticsBackend(ABC):
@@ -35,6 +36,21 @@ class AnalyticsBackend(ABC):
     def shutdown(self) -> None:
         """Flush pending events. Called on process exit."""
 
+    def get_user_feature_flags(
+        self,
+        user: User,  # pylint: disable=unused-argument
+    ) -> Mapping[UserFeatureFlag, bool | str | None]:
+        """Return a dict of feature flags for the given user."""
+        # We return an empty dict here by default to avoid a breaking change
+        # By making this method abstract.
+        return {}
+
+    def is_user_feature_enabled(
+        self, user: User, feature_name: UserFeatureFlag
+    ) -> bool:
+        """Check if a feature is enabled at the user level."""
+        return self.get_user_feature_flags(user).get(feature_name, False) is True
+
 
 class NoOpAnalytics(AnalyticsBackend):
     """Default backend: silently discards everything."""

src/backend/core/analytics/user_feature_flags.py

@@ -0,0 +1,9 @@
+"""Catalog of all analytics feature flags used by the backend."""
+
+from enum import StrEnum
+
+
+class UserFeatureFlag(StrEnum):
+    """All feature flags configured in the app."""
+
+    TRANSCRIPT_SUMMARY_ENABLED = "summary-enabled"