✨(backend) add ai_proxy

Add AI proxy to handle AI related requests
to the AI service.

src/backend/core/api/viewsets.py

@@ -475,6 +475,9 @@ class DocumentViewSet(
         Returns: JSON response with the translated text.
         Throttled by: AIDocumentRateThrottle, AIUserRateThrottle.
 
+    12. **AI Proxy**: Proxy an AI request to an external AI service.
+        Example: POST /api/v1.0/documents/<resource_id>/ai-proxy
+
     ### Ordering: created_at, updated_at, is_favorite, title
 
         Example:
@@ -1832,6 +1835,31 @@ class DocumentViewSet(
 
         return drf.response.Response(body, status=drf.status.HTTP_200_OK)
 
+    @drf.decorators.action(
+        detail=True,
+        methods=["post"],
+        name="Proxy AI requests to the AI provider",
+        url_path="ai-proxy",
+        throttle_classes=[utils.AIDocumentRateThrottle, utils.AIUserRateThrottle],
+    )
+    def ai_proxy(self, request, *args, **kwargs):
+        """
+        POST /api/v1.0/documents/<resource_id>/ai-proxy
+        Proxy AI requests to the configured AI provider.
+        This endpoint forwards requests to the AI provider and returns the complete response.
+        """
+        # Check permissions first
+        self.get_object()
+
+        if not settings.AI_FEATURE_ENABLED:
+            raise ValidationError("AI feature is not enabled.")
+
+        serializer = serializers.AIProxySerializer(data=request.data)
+        serializer.is_valid(raise_exception=True)
+
+        response = AIService().proxy(request.data)
+        return drf.response.Response(response, status=drf.status.HTTP_200_OK)
+
     @drf.decorators.action(
         detail=True,
         methods=["post"],