Fix manual trigger output schema (#8150)

- add schema for manual trigger
- split into sub functions
- handle case with no variables

packages/twenty-front/src/modules/workflow/components/WorkflowEditTriggerManualForm.tsx

@@ -87,6 +87,7 @@ export const WorkflowEditTriggerManualForm = ({
               ...trigger,
               settings: {
                 objectType: updatedObject,
+                outputSchema: {},
               },
             });
           }}