fix(functions): Set default functions region and add documentation - fix angular#1945 (angular#1946)

* fix(functions): Set default functions region and add documentation
* docs(functions): Fix display issue

Author: paulstelzer

docs/functions/functions.md

@@ -26,6 +26,29 @@ import { environment } from '../environments/environment';
 export class AppModule {}
 ```
 
+### Configure the Function region with the FunctionsRegionToken Injection Token
+
+Allow configuration of Function region with the `FunctionsRegionToken` Injection Token by adding it to the `providers` section of your `NgModule`. The default is `us-central1`.
+
+```ts
+import { NgModule } from '@angular/core';
+import { AngularFireFunctionsModule, FunctionsRegionToken } from '@angular/fire/functions';
+
+@NgModule({
+  imports: [
+    ...
+    AngularFireFunctionsModule,
+    ...
+  ],
+  ...
+  providers: [
+   { provide: FunctionsRegionToken, useValue: 'asia-northeast1' }
+  ]
+})
+export class AppModule {}
+
+```
+
 ### Injecting the AngularFireFunctions service
 
 Once the `AngularFireFunctionsModule` is registered you can inject the `AngularFireFunctions` service.

src/functions/functions.ts

@@ -5,6 +5,7 @@ import { FirebaseOptions, FirebaseAppConfig } from '@angular/fire';
 import { FirebaseFunctions, FirebaseOptionsToken, FirebaseNameOrConfigToken, _firebaseAppFactory, FirebaseZoneScheduler } from '@angular/fire';
 
 export const FunctionsRegionToken = new InjectionToken<string>('angularfire2.functions.region');
+export const FunctionsDefaultRegion = 'us-central1';
 
 @Injectable()
 export class AngularFireFunctions {
@@ -27,7 +28,7 @@ export class AngularFireFunctions {
 
     this.functions = zone.runOutsideAngular(() => {
       const app = _firebaseAppFactory(options, nameOrConfig);
-      return app.functions(region);
+      return app.functions(region || FunctionsDefaultRegion);
     });
 
   }