Generate unique Client Credentials for API access

Hello there!
I have a common use case I’d like to clarify, but I’m having trouble understanding the exact procedure from the documentation and other sources.

The scenario involves an API-based product. Each user can log in via a UI, set preferences, request client credentials to access the APIs, and eventually switch to a paid plan.

The user authentication through the UI is straightforward—I’m using the standard password flow.

What I’m unclear about is how to generate unique client credentials for each user.

The approach I thought about consisted of creating a different application per user but I suspect that wouldn’t scale due to entity limits.

Could you please provide some guidance on the best approach for this?