Create httl-required

camunda/camunda-modeler#4062 (comment)

docs/components/modeler/reference/modeling-guidance/rules/httl-required

@@ -0,0 +1,28 @@
+---
+id: httl-required
+title: HTTL (History Time To Live) required
+description: XXX.
+---
+
+import MarkerGuideline from "@site/src/mdx/MarkerGuideline";
+
+An [escalation event](../../../../bpmn/escalation-events/) must reference an escalation defined in the process. The referenced escalation must have a defined escalation code. To fix this problem, open the **Escalation** group in the properties panel, select or create an escalation, and specify its escalation code.
+
+Camunda 8.2 and later support catch-all events and do not require an escalation reference.
+
+## <MarkerGuideline.Invalid /> No escalation selected
+
+![No escalation selected](./img/escalation-reference/wrong-no-escalation-reference.png)
+
+## <MarkerGuideline.Invalid /> No escalation code specified
+
+![No escalation code specified](./img/escalation-reference/wrong-no-escalation-code.png)
+
+## <MarkerGuideline.Valid /> Escalation selected and escalation code specified
+
+![Escalation selected and escalation code specified](./img/escalation-reference/right.png)
+
+## Reference
+
+- [Escalation events](../../../../bpmn/escalation-events/)
+- [Rule source](https://github.com/camunda/bpmnlint-plugin-camunda-compat/blob/main/rules/camunda-cloud/escalation-reference.js)