feat(core): Add optional Error-Output (#7460)

Add an additional optional error output to which all items get sent that
could not be processed.
![Screenshot from 2023-10-18
17-29-15](https://github.com/n8n-io/n8n/assets/6249596/e9732807-ab2b-4662-a5f6-bdff24f7ad55)

Github issue / Community forum post (link here to close automatically):
https://community.n8n.io/t/error-connector-for-nodes/3094

https://community.n8n.io/t/error-handling-at-node-level-detect-node-execution-status/26791

---------

Co-authored-by: OlegIvaniv <me@olegivaniv.com>

packages/editor-ui/src/mixins/workflowHelpers.ts

@@ -649,6 +649,7 @@ export const workflowHelpers = defineComponent({
 				'credentials',
 				'disabled',
 				'issues',
+				'onError',
 				'notes',
 				'parameters',
 				'status',
@@ -725,14 +726,16 @@ export const workflowHelpers = defineComponent({
 				}
 			}
 
-			// Save the disabled property and continueOnFail only when is set
+			// Save the disabled property, continueOnFail and onError only when is set
 			if (node.disabled === true) {
 				nodeData.disabled = true;
 			}
 			if (node.continueOnFail === true) {
 				nodeData.continueOnFail = true;
 			}
-
+			if (node.onError !== 'stopWorkflow') {
+				nodeData.onError = node.onError;
+			}
 			// Save the notes only if when they contain data
 			if (![undefined, ''].includes(node.notes)) {
 				nodeData.notes = node.notes;