Buyer should be able to make a payment

The backend needs to handle the payment process using the Stripe API. This includes:

Successful Payment:

[ ] GIVEN a POST request for payment
[ ] WHEN the requesting user/token is a buyer and the request body is validated (order details, payment information)
[ ] The payment is processed using the Stripe API.
[ ] The order status in the database is updated to "paid" (or equivalent).
[ ] An order confirmation email is sent to the frontend containing:
[ ] Order number
[ ] Total cost
[ ] Expected delivery date (if available)
[ ] A success response is sent to the frontend.

Failed Validation or Invalid User:

[ ] WHEN the request body fails any validation checks or the token is not associated with a buyer role
[ ] A 4XX response message is sent to the frontend describing the validation error (e.g., missing field, invalid data format).

1. Setup:

Stripe Account: Create a Stripe account and obtain your API keys (test or live, depending on your development stage). Store them securely using environment variables.
Stripe Library: Install the Stripe Node.js library using npm

2. API Endpoint Design:

Create a POST endpoint: Define a POST endpoint in your Node.js backend to handle payment requests.
Request Body: The request body should contain validated data for:
Order details (order ID, total amount, etc.)
Payment information (card details or token)

3. User Authentication and Role Validation:

Authentication: Implement a mechanism to authenticate the user and verify their role. This could involve token-based authentication where the token is passed in the request header.
Role Check: Ensure only users with the "buyer" role can access the payment endpoint. Return a 403 Forbidden error for unauthorized users.

4. Payment Processing:

Stripe Integration: Use the Stripe library to interact with the Stripe API.
Payment Charge: Create a charge object on the Stripe server representing the payment amount.
Error Handling: Handle potential Stripe API errors and return appropriate error responses to the frontend (e.g., 4XX errors for declined cards or insufficient funds).

5. Order Status Update:

Upon successful payment, update the order status in your database to reflect the payment as "paid" (or a similar state).

6. Confirmation Email:(optional)

Content: Generate a confirmation email containing order details (order number, total cost, delivery date, etc.).
Sending: Send the confirmation email to the buyer's email address using a Node.js email library.

7. Response to Frontend:

Success: Upon successful payment processing, order status update, and email sending, send a success response to the frontend confirming the payment.
Failure: In case of any errors, return an appropriate error response with a detailed message.

atlp-rwanda / knights-ecomm-be