Add basic concepts for event bus, and implement in request and model

src/http/kernel/module/InjectRequestEventBusHTTPModule.ts

@@ -0,0 +1,28 @@
+import {HTTPKernelModule} from '../HTTPKernelModule'
+import {Inject, Injectable} from '../../../di'
+import {HTTPKernel} from '../HTTPKernel'
+import {Request} from '../../lifecycle/Request'
+import {EventBus} from '../../../event/EventBus'
+import {PropagatingEventBus} from '../../../event/PropagatingEventBus'
+
+/**
+ * HTTP kernel module that creates a request-specific event bus
+ * and injects it into the request container.
+ */
+@Injectable()
+export class InjectRequestEventBusHTTPModule extends HTTPKernelModule {
+    @Inject()
+    protected bus!: EventBus
+
+    public static register(kernel: HTTPKernel): void {
+        kernel.register(this).first()
+    }
+
+    public async apply(request: Request): Promise<Request> {
+        const bus = <PropagatingEventBus> this.make(PropagatingEventBus)
+        bus.connect(this.bus)
+
+        request.purge(EventBus).registerProducer(EventBus, () => bus)
+        return request
+    }
+}