feat: Add getServiceScopes method to GapicClientTrait (#9372)

Author: cy-yun

Gax/src/GapicClientTrait.php

@@ -157,6 +157,16 @@ public function prependMiddleware(callable $middlewareCallable): void
         $this->prependMiddlewareCallables[] = $middlewareCallable;
     }
 
+    /**
+     * Get the default scopes required by the service.
+     *
+     * @return array
+     */
+    public static function getServiceScopes(): array
+    {
+        return self::$serviceScopes;
+    }
+
     /**
      * Initiates an orderly shutdown in which preexisting calls continue but new
      * calls are immediately cancelled.

Gax/tests/Unit/GapicClientTraitTest.php

@@ -1882,6 +1882,14 @@ private function createTransport(
 
         $this->assertTrue($gapic->hasEmulator);
     }
+
+    public function testGetServiceScopes()
+    {
+        $this->assertEquals(
+            ['default-scope-1', 'default-scope-2'],
+            DefaultScopeAndAudienceGapicClient::getServiceScopes()
+        );
+    }
 }
 
 class StubGapicClient