feat: support first chance to define routes (#931) Thanks to @jsw-

* feat: support first chance to define routes

* Empty commit to trigger a CI rerun

Author: jcw-

packages/cubejs-server/index.d.ts

@@ -5,6 +5,7 @@ import http from 'http';
 
 export interface CreateOptions extends CoreCreateOptions {
   webSockets?: boolean;
+  initApp?(app: express.Application): void | Promise<void>;
 }
 
 declare class CubejsServer {

packages/cubejs-server/index.js

@@ -12,6 +12,7 @@ class CubejsServer {
     this.webSockets = config.webSockets;
     this.redirector = null;
     this.server = null;
+    this.initApp = config.initApp;
   }
 
   async listen(options = {}) {
@@ -29,6 +30,10 @@ class CubejsServer {
       app.use(require("cors")());
       app.use(bodyParser.json({ limit: "50mb" }));
 
+      if (this.initApp) {
+        await this.initApp(app);
+      }
+
       await this.core.initApp(app);
 
       return new Promise((resolve, reject) => {