Ideas to control the OTP or Suscriptions?

Hi everyone,

I am new developing skills with VF.

I have a doubt, if I wanted to monetize my skill, how do I do it from my skill to know which user bought content? or some feature?

How do I distinguish between those who bought and those who did not buy?

Or so does the Amazon platform?

Any ideas or guides you can give me. I’m not clear, who and how this control can be follow.

Thank you so much!

first, as a guide for basic design for in-skill purchase,

second, basic qas for ISP is here. this might cover some of your questions.