Implement API V2 marketplace endpoints

What problem are you facing?

The current implementation of the SDK is missing the api/v2 endpoints related to marketplace:

• POST /api/v2/marketplace/azure/billing (Used by admin to bill user's Azure account with the cost of SonarQube Server license.)

How could the SonarQube SDK help solve your problem?

• Implement those RESTful endpoints
• Add unit tests for them
• Add e2e tests for them