Function KeyHandler

KeyHandler<T extends ClassType = ClassType>(): ClassDecorator
Class decorator: mark a class as a light-router handler container.

The class is registered as a container service and contributed to stone.keyRouting.handlers; the KeyRoutingServiceProvider resolves it (with dependency injection) and wires its @OnKey methods into the key-router.
Type Parameters
- T extends ClassType = ClassType
Returns ClassDecorator
A class decorator.
Example
```
@KeyHandler()
export class Handlers {
  @OnKey('order.shipped') onShipped (payload) { ... }
}
```