How a rate plan can be created and associated during subscription creation using REST API

We are having use case scenario where subscriptions are getting created using REST API from third party system. Even pricing configuration is also done there outside Oracle Fusion.

We are having usage related use cases (like allowances, commitments) where we need Rate Plans to get associated with the subscription products to create usage events.

Can anyone please help us here with some sample REST API payload to create and associate Rate Plan while creating subscriptions?