Adding an entrypoint for firebase-admin-node (#216)

* Expose init function for admin SDK

* Fixing issues with module.exports for @firebase/database

* [AUTOMATED]: Prettier Code Styling

* Refactor namespaces -> namespace

Author: jshcrowthe

packages/database/index.node.ts

@@ -25,6 +25,28 @@ import * as TEST_ACCESS from './src/api/test_access';
 import { isNodeSdk } from '@firebase/util';
 import './src/nodePatches';
 
+/**
+ * A one off register function which returns a database based on the app and
+ * passed database URL.
+ * 
+ * @param app A valid FirebaseApp-like object
+ * @param url A valid Firebase databaseURL 
+ */
+export function initStandalone(app, url) {
+  return {
+    instance: RepoManager.getInstance().databaseFromApp(app, url),
+    namespace: {
+      Reference,
+      Query,
+      Database,
+      enableLogging,
+      INTERNAL,
+      ServerValue: Database.ServerValue,
+      TEST_ACCESS
+    }
+  };
+}
+
 export function registerDatabase(instance: FirebaseNamespace) {
   // Register the Database Service with the 'firebase' namespace.
   const namespace = instance.INTERNAL.registerService(
@@ -45,7 +67,7 @@ export function registerDatabase(instance: FirebaseNamespace) {
   );
 
   if (isNodeSdk()) {
-    module.exports = namespace;
+    module.exports = Object.assign({}, namespace, { initStandalone });
   }
 }