feat(component): allow to specify a base url for loading recaptcha

"google.com" domain might be unavailable in certain countries, so we're adding the ability to specify a different base url for the script.

Closes #101

README.md

@@ -24,6 +24,7 @@ A simple, configurable, easy-to-start component for handling reCAPTCHA.
    * [Working with invisible reCAPTCHA](#example-invisible)
    * [Resizing](#example-resizing)
    * [SystemJS configuration](#example-systemjs)
+   * [Loading from a different location](#example-different-url)
 
 ## <a name="installation"></a>Installation
 
@@ -339,3 +340,20 @@ To configure the package to work with SystemJS, you would configure it approxima
   });
 })();
 ```
+
+### <a name="example-different-url"></a>Loading from a different location
+
+Since `"google.com"` domain might be unavailable in some countries, reCAPTCHA core team has a solution for that - using `"recaptcha.net"` domain. You can configure the component to use that by providing the `RECAPTCHA_BASE_URL` token, for example:
+
+```javascript
+import { RECAPTCHA_BASE_URL } from 'ng-recaptcha';
+
+@NgModule({
+  providers: [
+    {
+      provide: RECAPTCHA_BASE_URL,
+      useValue: 'https://recaptcha.net/recaptcha/api.js', // use recaptcha.net script source for some of our users
+    },
+  ],
+}) export class MyModule { }
+```

index.ts

@@ -1,4 +1,4 @@
 export { RecaptchaComponent } from './recaptcha/recaptcha.component';
-export { RecaptchaLoaderService, RECAPTCHA_LANGUAGE } from './recaptcha/recaptcha-loader.service';
+export { RecaptchaLoaderService, RECAPTCHA_LANGUAGE, RECAPTCHA_BASE_URL } from './recaptcha/recaptcha-loader.service';
 export { RecaptchaModule } from './recaptcha/recaptcha.module';
 export { RECAPTCHA_SETTINGS, RecaptchaSettings } from './recaptcha/recaptcha-settings';

recaptcha/recaptcha-loader.service.ts

@@ -9,6 +9,7 @@ import {
 import { BehaviorSubject, Observable, of } from 'rxjs';
 
 export const RECAPTCHA_LANGUAGE = new InjectionToken<string>('recaptcha-language');
+export const RECAPTCHA_BASE_URL = new InjectionToken<string>('recaptcha-base-url');
 
 @Injectable()
 export class RecaptchaLoaderService {
@@ -22,13 +23,17 @@ export class RecaptchaLoaderService {
 
   /** @internal */
   private language: string;
+  /** @internal */
+  private baseUrl: string;
 
   constructor(
     // tslint:disable-next-line:no-any
     @Inject(PLATFORM_ID) private readonly platformId: any,
     @Optional() @Inject(RECAPTCHA_LANGUAGE) language?: string,
+    @Optional() @Inject(RECAPTCHA_BASE_URL) baseUrl?: string,
   ) {
     this.language = language;
+    this.baseUrl = baseUrl;
     this.init();
     this.ready = isPlatformBrowser(this.platformId) ? RecaptchaLoaderService.ready.asObservable() : of();
   }
@@ -46,7 +51,8 @@ export class RecaptchaLoaderService {
       const script = document.createElement('script') as HTMLScriptElement;
       script.innerHTML = '';
       const langParam = this.language ? '&hl=' + this.language : '';
-      script.src = `https://www.google.com/recaptcha/api.js?render=explicit&onload=ng2recaptchaloaded${langParam}`;
+      const baseUrl = this.baseUrl || 'https://www.google.com/recaptcha/api.js';
+      script.src = `${baseUrl}?render=explicit&onload=ng2recaptchaloaded${langParam}`;
       script.async = true;
       script.defer = true;
       document.head.appendChild(script);