refactor(trigger): streamline workflow argument handling in DraftWorkflowTriggerNodeApi

- Simplified retrieval of workflow arguments by directly accessing event.workflow_args.
- Removed unnecessary conditional checks for user inputs, ensuring cleaner code.
- Enhanced TriggerEventNode to use deepcopy for user inputs to prevent unintended mutations.

api/core/workflow/nodes/trigger_plugin/trigger_event_node.py

@@ -1,4 +1,5 @@
 from collections.abc import Mapping
+from copy import deepcopy
 from typing import Any, Optional
 
 from core.workflow.entities.workflow_node_execution import WorkflowNodeExecutionMetadataKey, WorkflowNodeExecutionStatus
@@ -65,7 +66,7 @@ class TriggerEventNode(Node):
         """
 
         # Get trigger data passed when workflow was triggered
-        inputs = dict(self.graph_runtime_state.variable_pool.user_inputs)
+        inputs = deepcopy(self.graph_runtime_state.variable_pool.user_inputs)
         metadata = {
             WorkflowNodeExecutionMetadataKey.TRIGGER_INFO: {
                 "provider_id": self._node_data.provider_id,