DynamicTheme support in Vaadin 25+ for multi-version add-ons

[javier-godoy]

Currently (#141), the DynamicTheme feature requires initialization in the AppShellConfigurator of the application.

public class AppShellConfiguratorImpl implements AppShellConfigurator {

  @Override
  public void configurePage(AppShellSettings settings) {
    if (DynamicTheme.isFeatureSupported()) {
      DynamicTheme.LUMO.initialize(settings);
    }
  }

}

Add-on compatibility across Vaadin versions requires specific commons-demo versions and has the following architectural limitations:

• Vaadin 24–25: demo uses commons-demo 5.x, which supports @DynamicTheme.
• Vaadin 23: demo uses commons-demo 3.x. The @DynamicTheme annotation is not present in this version.
• Vaadin 14: demo uses commons-demo 3.x. Cannot implement an AppShellConfigurator, as it was introduced in later versions of the framework.