Add resolved suggestions to CDS Hooks cards for nested actions

[ft9dipesh]

Problem

CdsResponseEncoderService.resolveAction resolves each child action of a selectionBehavior action via resolveSuggestion, but never adds the result to the card:

if (action.hasSelectionBehavior()) {
    card.setSelectionBehaviour(action.getSelectionBehavior());
    action.getAction().forEach(this::resolveSuggestion);
}

Any PlanDefinition with nested actions therefore produces a card with selectionBehavior set and no suggestions.

Fix

action.getAction().forEach(child -> card.addSuggestion(resolveSuggestion(child)));

Test

Added testResolveAction_shouldAddSuggestionsForNestedActionsWhenSelectionBehaviorIsSet to ResponseEncoderMethodResolveActionTest.