No information about major/minor for glyph. in wow classic

wow classic added information about glyphs as Wrath of the Lich King is coming soon.
There are two types of glyphs: major and minor. However, in the existing item API, there is no value to distinguish it.
There is no distinction between item_class_id and item_subclass_id, and even when I look at the preview, I do not see a value that can be distinguished.
please add this