Liking system with firebase (Question)

Hey everyone, has anyone made any kind of liking system with firebase so i can understand how is best to structure my data.
More specifically in my app admin uploads products and users can like a product and when they do so it appears in their profile (which is open for everyone to see).
My main question is if its possible to but the liked product ids as fields in a document, or i should make each liked product id a different document.

I hope you can understand what im trying to make, feel free to tell me your opinion and ask any questions.