fix: Add integration brain to subscription route (#2410)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

backend/routes/subscription_routes.py

@@ -21,7 +21,13 @@
     SubscriptionInvitationService,
     resend_invitation_email,
 )
+from modules.brain.repository import (
+    IntegrationBrain,
+)
 from routes.headers.get_origin_header import get_origin_header
+from logger import get_logger
+
+logger = get_logger(__name__)
 
 subscription_router = APIRouter()
 subscription_service = SubscriptionInvitationService()
@@ -30,6 +36,7 @@
 brain_user_service = BrainUserService()
 brain_service = BrainService()
 api_brain_definition_service = ApiBrainDefinitionService()
+integration_brains_repository = IntegrationBrain()
 
 
 @subscription_router.post(
@@ -249,7 +256,18 @@ async def accept_invitation(
             rights=invitation["rights"],
             is_default_brain=False,
         )
+        shared_brain = brain_service.get_brain_by_id(brain_id)
+        integration_brain = integration_brains_repository.get_integration_brain(
+            brain_id=brain_id,
+        )
+        integration_brains_repository.add_integration_brain(
+            brain_id=brain_id,
+            user_id=current_user.id,
+            integration_id=integration_brain.integration_id,
+            settings=integration_brain.settings,
+        )
     except Exception as e:
+        logger.error(f"Error adding user to brain: {e}")
         raise HTTPException(status_code=400, detail=f"Error adding user to brain: {e}")
 
     try: