Fix: payment callbacks

[amowogbaje]

Description

Implemented an endpoint to make payment

Motivation and Context

To establish relationship between payment, organisations and subscriptions

How Has This Been Tested?

Tested the endpoint using Postman:

• Sent GET and POST requests with valid and invalid IDs to ensure correct responses.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.