Feat: Integration of the Nevermined payments library

[r-marques]

Nevermined Integration

• App at https://nevermined.app/
• Docs at https://docs.nevermined.app

Overview

This pr is meant to be an example of how to integrate the nevermined payments library with xpander.ai in order to monetize agent calls.

Builder Flow

1. The builder creates a Nevermined API key
2. The builder registers the agent on Nevermined
3. The builder creates a credit based pricing plan and associates it to the agent
4. The builder validates the subscriber request before making a call to the agent
5. The builder redeems the credits in case of a successful call.

Subscriber Flow

1. The subscriber buys the plan for the agent
2. The subscriber gets an access token to make an authorized call to the agent