Update workflow version struct (#6716)

We want to avoid the nested structure of active pieces. Steps to execute
will now be separated from the trigger. It will be an array executed
sequentially.

For now a step can only be an action. But at some point it will also be
a branch or a loop

packages/twenty-server/src/modules/workflow/workflow-trigger/utils/assert-workflow-version-is-valid.ts

@@ -27,9 +27,9 @@ export function assertWorkflowVersionIsValid(
     );
   }
 
-  if (!workflowVersion.trigger.nextAction) {
+  if (!workflowVersion.steps || workflowVersion.steps.length === 0) {
     throw new WorkflowTriggerException(
-      'No next action provided in trigger',
+      'No steps provided in workflow version',
       WorkflowTriggerExceptionCode.INVALID_WORKFLOW_TRIGGER,
     );
   }