Vaadin 25 migration work needed

[stefanuebe]

Just tested the CBL with Vaadin 25 at a customer migration preview. Fails due to the usage of elemental Json.

Caused by: java.lang.NoSuchMethodError: 'void com.vaadin.flow.data.provider.CompositeDataGenerator.generateData(java.lang.Object, elemental.json.JsonObject)'
	at org.vaadin.addons.componentfactory.ComboBoxLight.reset(ComboBoxLight.java:160)
	at org.vaadin.addons.componentfactory.ComboBoxLight.setDataProvider(ComboBoxLight.java:301)
	at com.vaadin.flow.data.binder.HasDataProvider.setItems(HasDataProvider.java:50)
	at de.csc_dd.gui.refapp.vaadin.nativevaadin.issues.DlgNative_147930_ComboboxOverlayWidth.<init>(DlgNative_147930_ComboboxOverlayWidth.java:62)
	at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62)
	... 93 more

[TatuLund]

Fails due to the usage of elemental Json.

This will be common issue with many add-ons, thanks for spotting.