Move EventBus into its own file

src/event-bus/event-bus.ts

+import { EventType } from './types';
+import { NotImplementedError } from 'funfix';
+
+export abstract class EventBus {
+    // register the following:
+    // - eventsToHandle - a list of events you will publish/subscribe to
+    // - serviceName - used when subscribing to generate a unique queue for holding
+    // incoming messages of the form: `consumer__${eventType}__${serviceName}`
+    constructor(readonly eventsToHandle: EventType[], readonly serviceName: string) {}
+    destroy(): Promise<void> {
+        throw new NotImplementedError('destroy() on EventBus');
+    }
+}

src/event-bus/types.ts

+// Abstract Message Queue - types and interfaces
+
+/**
+ * TODO: Once agreed, add these to DefinitelyTyped so they can be shared.
+ */
+
+export type EventType = string;
+
+export interface Event<T extends object> {
+    readonly eventType: EventType;
+    readonly id: string; // Generated when the event is emitted
+    readonly created: Date;
+    readonly payload: T; // The actual data the event is carrying.
+    // version:  has been removed - so we can remain weakly typed
+    // context: has also been removed - if you need information about the origin
+    //          source of the event then put it in the payload.
+}
+
+export interface EventPublisher {
+    // Promise<boolean> should this become void | exception? we only need to know if something went wrong
+    publish<T extends object>(event: Event<T>): Promise<boolean>;
+}
+
+export interface EventSubscriber {
+    // handler: returns whether or not we should ack the message
+    subscribe<T extends object>(eventType: string, handler: (event: Event<T>) => Promise<boolean>): void;
+}
+
+// This isn't generic enough
+export interface EventConfig {
+    url: string;
+}