feat(hp): add onStageChange callback (#5165)

platform/core/src/services/HangingProtocolService/HangingProtocolService.ts

@@ -1064,6 +1064,11 @@ export default class HangingProtocolService extends PubSubService {
         throw new Error(`Can't find applicable stage ${protocol.id} ${options?.stageIndex}`);
       }
       this.stageIndex = stage as number;
+
+      if (this.protocol?.callbacks?.onStageChange) {
+        this._commandsManager.run(this.protocol.callbacks.onStageChange);
+      }
+
       this._updateViewports(options);
     } catch (error) {
       console.log(error);

platform/core/src/types/HangingProtocol.ts

@@ -293,6 +293,8 @@ export type ProtocolNotifications = {
   // and all viewport data includes a designated display set. This command
   // will run on every stage's initial layout.
   onViewportDataInitialized?: Command[];
+  // This set of commands is executed before the stage change is applied
+  onStageChange?: Command[];
 };
 
 /**