Move EventBus into its own file

src/event-bus/index.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;
-}
-
-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> {
-        return Promise.resolve();
-    }
-}
-
-// This isn't generic enough
-export interface EventConfig {
-    url: string;
-}
+export * from './event-bus';
+export * from './types';