feat(decide): added decision API

src/backend/api/v1/decision/endpoints.py

@@ -0,0 +1,34 @@
+from http import HTTPStatus
+
+from django.http import HttpRequest
+from ninja import Router
+
+from api.v1.decision.schemas import DecisionIn, DecisionOut, SingleDecisionOut
+from apps.decision.services import decide_for_flag
+
+router = Router(tags=["decision"])
+
+
+@router.post(
+    "",
+    response={HTTPStatus.OK: DecisionOut},
+    summary="Get decisions for feature flags",
+    description=(
+        "Resolve feature flag values for a given subject. "
+        "Returns default values when no active experiment applies, "
+        "or experiment variant values when the subject is assigned."
+    ),
+)
+def decide(
+    request: HttpRequest,
+    payload: DecisionIn,
+) -> tuple[HTTPStatus, DecisionOut]:
+    decisions = []
+    for flag_key in payload.flags:
+        result = decide_for_flag(
+            flag_key=flag_key,
+            subject_id=payload.subject_id,
+            subject_attributes=payload.subject_attributes,
+        )
+        decisions.append(SingleDecisionOut(**result))
+    return HTTPStatus.OK, DecisionOut(decisions=decisions)