Buy a subscription

[r-marques]

Describe how to buy a subscription using the sdk

1. instantiate the sdk
2. login to nevermined
3. get the subscription details
4. buy the subscription
5. show that the buyer is an holder of the subscription
6. show that the buyer can access the datasets associated with the subscription

Reference: https://github.com/nevermined-io/sdk-js/blob/main/integration/external/Datasets.e2e.test.ts