fix(volcengine/iam): Handle TrustPolicyDocument field as string type

Ensure the TrustPolicyDocument field retrieved from the API is of string type to avoid type errors during subsequent processing

(cherry picked from commit ba0d94d2705c0916d18ee0e824244373dfaceba7)

Author: liulei.88

agentkit/apps/agent_server_app/agent_server_app.py

@@ -102,10 +102,7 @@ async def _invoke_compat(request: Request):
             user_id = (
                 headers.get("user_id") or headers.get("x-user-id") or "agentkit_user"
             )
-            session_id = (
-                headers.get("session_id")
-                or ""
-            )
+            session_id = headers.get("session_id") or ""
 
             # Determine app_name from loader
             app_names = self.server.agent_loader.list_agents()

agentkit/toolkit/volcengine/iam.py

@@ -221,7 +221,13 @@ def get_role(self, role_name: str) -> Optional[GetRoleResponse]:
                 data="{}",
             )
             response_data = json.loads(res)
-            return GetRoleResponse(**response_data.get("Result", {}))
+            result_data = response_data.get("Result", {})
+            role_data = result_data.get("Role")
+            if isinstance(role_data, dict):
+                tpd = role_data.get("TrustPolicyDocument")
+                if isinstance(tpd, dict):
+                    role_data["TrustPolicyDocument"] = json.dumps(tpd)
+            return GetRoleResponse(**result_data)
         except Exception as e:
             # If role not found, return None
             if "RoleNotExist" in str(e) or "NotFound" in str(e) or "404" in str(e):