[FIX]: Add Expected Data Samples To Docs For All Billing Plan Endpoints

[chimeziriobioha]

Description

Currently, all billing plan endpoints do not display the expected data samples on the backend documentation for the frontend developers to reference when building relevant UI. This can slow down development due to back and forth between backend and frontend devs to verbally and manually communicate data structure. This ticket seeks to update the docs and address this problem.

Expected Behavior

Frontend developers and others viewing the backend docs should be able to know exactly what to expect from each endpoint.

Screenshots

Current Response Schemas

Acceptance Criteria

• Stick to the changes required to fix the particular bug mentioned in description.
• Do not change other people's code without appropriate permission.

Testing

• Write test for all updates requiring one
• Ensure all existing tests passes [without tampering], alongside the new ones added