feat: initial mini simple event sourcing for pending application updates

domain/events/ApplicationUpdateStarted.ts

@@ -0,0 +1,14 @@
+type ApplicationUpdateStartedPayload = {
+  id: string;
+  newVersion: string;
+};
+
+export class ApplicationUpdateStarted
+  implements DomainEvent<ApplicationUpdateStartedPayload>
+{
+  readonly type = "ApplicationUpdateStarted" as const;
+  constructor(
+    public readonly payload: ApplicationUpdateStartedPayload,
+    public readonly createdAt: Date
+  ) {}
+}