fix(google): config google application credentials

- Fix #140
- Fix #176

Author: imdhemy

config/liap.php

@@ -30,6 +30,17 @@
      */
     'google_play_package_name' => env('GOOGLE_PLAY_PACKAGE_NAME', 'com.some.thing'),
 
+    /*
+     |--------------------------------------------------------------------------
+     | Google Application Credentials
+     |--------------------------------------------------------------------------
+     |
+     | This value is the path to the Google Application Credentials file.
+     | @see https://imdhemy.com/laravel-iap-docs/docs/credentials/google-play
+     |
+     */
+    'google_application_credentials' => env('GOOGLE_APPLICATION_CREDENTIALS', null),
+
     /*
      |--------------------------------------------------------------------------
      | App Store Password

src/ServiceProviders/LiapServiceProvider.php

@@ -20,6 +20,7 @@
 use Imdhemy\Purchases\Subscription;
 use Lcobucci\JWT\Decoder;
 use Lcobucci\JWT\Encoding\JoseEncoder;
+use RuntimeException;
 
 /**
  * Laravel Iap service provider
@@ -112,6 +113,14 @@ public function register(): void
     private function registerConfig(): void
     {
         $this->mergeConfigFrom(self::CONFIG_PATH, self::CONFIG_KEY);
+
+        $googleCredentials = config(self::CONFIG_KEY . '.google_application_credentials');
+        if ($googleCredentials !== null) {
+            if (! file_exists($googleCredentials)) {
+                throw new RuntimeException("Google Application Credentials file not found at $googleCredentials");
+            }
+            putenv('GOOGLE_APPLICATION_CREDENTIALS=' . $googleCredentials);
+        }
     }
 
     /**