feat: Service API - add end-user lookup endpoint (#32015)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/controllers/service_api/end_user/__init__.py

@@ -0,0 +1,3 @@
+from . import end_user
+
+__all__ = ["end_user"]

api/controllers/service_api/end_user/end_user.py

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+from uuid import UUID
+
+from flask_restx import Resource
+
+from controllers.service_api import service_api_ns
+from controllers.service_api.end_user.error import EndUserNotFoundError
+from controllers.service_api.wraps import validate_app_token
+from fields.end_user_fields import EndUserDetail
+from models.model import App
+from services.end_user_service import EndUserService
+
+
+@service_api_ns.route("/end-users/<uuid:end_user_id>")
+class EndUserApi(Resource):
+    """Resource for retrieving end user details by ID."""
+
+    @service_api_ns.doc("get_end_user")
+    @service_api_ns.doc(description="Get an end user by ID")
+    @service_api_ns.doc(
+        params={"end_user_id": "End user ID"},
+        responses={
+            200: "End user retrieved successfully",
+            401: "Unauthorized - invalid API token",
+            404: "End user not found",
+        },
+    )
+    @validate_app_token
+    def get(self, app_model: App, end_user_id: UUID):
+        """Get end user detail.
+
+        This endpoint is scoped to the current app token's tenant/app to prevent
+        cross-tenant/app access when an end-user ID is known.
+        """
+
+        end_user = EndUserService.get_end_user_by_id(
+            tenant_id=app_model.tenant_id, app_id=app_model.id, end_user_id=str(end_user_id)
+        )
+        if end_user is None:
+            raise EndUserNotFoundError()
+
+        return EndUserDetail.model_validate(end_user).model_dump(mode="json")

api/controllers/service_api/end_user/error.py

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+from libs.exception import BaseHTTPException
+
+
+class EndUserNotFoundError(BaseHTTPException):
+    error_code = "end_user_not_found"
+    description = "End user not found."
+    code = 404