Managing GPT users - Auth & Monetization

How are you currently looking at the best setup to authenticate and monetize users for your custom GPTs?
How would you go about monitoring the actual usage of your GPTs?

GPTs monetisation will be in the form of revenue share for the most popular entries.

I would assume that you might also want to add more endpoint-specific monetization and usage schemes to your GPTs

I am sure people will try, but monetisation is currently via revenue share when the GPT store opens.