Google Analytics (particularly version 4, "GA4") has various predefined events, each with its own parameters. E.g. the purchase event has an items parameter, which contains data such as item_id and item_name for each purchased item. JS code on a website can send these events and pass the extra data, and I can actually see the data in the "Analysis hub" in the Google Analytics interface.
Is there a way to also fetch this extra data using the Google Analytics Data API? There is a way to retrieve some predefined dimensions and also "custom dimensions" (via customEvent:parameter_name), but e.g. purchase item data doesn't seem to be a part of that.
Do I have to define custom dimensions (e.g. a purchasedProductId) and send them in addition to the items parameter, if I want to access this data via API?