code: @Nonnull
    public PreloadFont getOrAddEmbeddingPreloadFont (@Nonnull final IHasFontResource aFontResProvider)
    {
      ValueEnforcer.notNull (aFontResProvider, "FontResProvider");
      return getOrAddEmbeddingPreloadFont (aFontResProvider.getFontResource ());
    }
docs: Create and add a new embedding {@link PreloadFont} if it is not yet
  contained.
  
  @param aFontResProvider
  The font resource provider to be added for embedding. May not be
  <code>null</code>.
  @return The created {@link PreloadFont}. Never <code>null</code>.