code: public static Metadata<Extension> loadExtension(String extensionClass, ClassLoader classloader) {
          Class<? extends Extension> serviceClass = loadClass(Extension.class, extensionClass, classloader);
          if (serviceClass == null) {
              return null;
          }
          Extension serviceInstance = prepareInstance(serviceClass);
          if (serviceInstance == null) {
              return null;
          }
          return new MetadataImpl<Extension>(serviceInstance, extensionClass);
      }
docs: Create the extension and return a metadata for the extension
  
  @param extensionClass extension class name
  @param classloader the class loader that loads the extension
  @return