Authorization Policies like AWS in .NET Core

Question

Background
We have created a permissions based system which is driven by the database and each user can have group permissions or individual permissions to access a particular action method on the controller.

This is controlled by attributes and authorization policies and handlers in the current system.

Required

The above gives almost fine grained control to who can do what.

Is there any articles or examples of a system where the policy can be created using JSON like in AWS IAM Policies or Azure User policies which are JSON based.

Appreciate any ideas.