feat: implement payment intent creation endpoint (Issue #8)

[GEEKYFOCUS]

Overview

This PR implements the Payment Intent Creation endpoint for Stellar Pay, enabling merchants to create payment intents for Stellar network transactions. The implementation includes complete API endpoints with JWT authentication, comprehensive input validation, and a full test suite with 22 passing tests.

Related Issue

Closes #8

Changes

🎯 Payment Intent API Implementation

• [CREATE] apps/api/src/payments/payments.controller.ts

  • Implemented three endpoints: POST /payments, GET /payments, GET /payments/:paymentId
  • Added JWT authentication via @CurrentMerchant() decorator
  • Proper HTTP status codes and error handling

• [CREATE] apps/api/src/payments/payments.service.ts

  • Implemented createPaymentIntent() with UUID generation
  • Unique payment reference format: PYMT-{MERCHANT}-{TIMESTAMP}-{RANDOM}
  • Checkout URL generation with secure routing
  • Support for multiple assets: USDC, ARS, BRL, COP, MXN, XLM

• [CREATE] apps/api/src/payments/payments.module.ts

  • NestJS module registration with ConfigModule import
  • Proper dependency injection setup

📋 Data Transfer Objects

• [CREATE] apps/api/src/payments/dto/create-payment-intent.dto.ts

  • Input validation with class-validator
  • Amount, asset, description, and metadata fields
  • Type-safe enum for supported assets

• [CREATE] apps/api/src/payments/dto/payment-intent-response.dto.ts

  • Response serialization with @expose decorators
  • Complete payment intent data structure

🧪 Comprehensive Test Suite

• [CREATE] apps/api/src/payments/payments.controller.spec.ts

  • 10 integration tests for all three endpoints
  • Authentication and authorization tests
  • Error handling verification

• [CREATE] apps/api/src/payments/payments.service.spec.ts

  • 12 unit tests for business logic
  • Payment reference generation validation
  • Merchant isolation verification

🔧 Core Module Updates

• [MODIFY] apps/api/src/app.module.ts

  • Added ConfigModule.forRoot() for environment configuration
  • Registered PaymentsModule

• [MODIFY] apps/api/src/main.ts

  • Added global ValidationPipe with strict mode
  • Request/response auto-transformation

• [MODIFY] apps/api/package.json

  • Added @nestjs/config, uuid, class-validator, class-transformer dependencies
  • Added dev:api script for development

🛠️ Development & Testing Tools

• [CREATE] apps/api/generate-test-token.mjs

  • JWT token generator for endpoint testing (no external dependencies)
  • Ready-to-copy curl commands

• [CREATE] DEV_SETUP.md

  • Comprehensive development environment guide
  • Testing instructions with example requests

• [MODIFY] turbo.json

  • Optimized dev task configuration
  • Fixed Next.js lock file conflicts

Verification Results

Acceptance Criteria	Status	Details
Payment intent creation endpoint implemented	✅	POST /payments fully functional
JWT authentication enforced	✅	@CurrentMerchant decorator validates tokens
Input validation working	✅	class-validator DTO validation
All tests passing	✅	22/22 tests passing (3 suites)
Build successful	✅	0 TypeScript errors
Lint passing	✅	0 ESLint errors in API code
Unique payment references generated	✅	Format: PYMT-{MERCHANT}-{TIMESTAMP}-{RANDOM}
Merchant isolation enforced	✅	Each merchant can only see their own payments

How to Test

1. Generate Test Token

cd apps/api
node generate-test-token.mjs

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[GEEKYFOCUS]

Hello Maintainer.
I pushed an update few hours ago. Kindly review the PR, so the issue can be closed.
I await your swift response. Thanks

[MissBlue00]

@GEEKYFOCUS ci/cd checks failed and there are merge conflicts, please resolve

[GEEKYFOCUS]

I just resolved a conflict with base, kindly review the changes, so the issue can be closed.
I await your swift response, thanks

[GEEKYFOCUS]

Hello Maintainer.
Kindly review the PR, so the issue can be closed. Thanks

[GEEKYFOCUS]

Hi Maintainer.
All conflict been resolved, kindly review my PR so the conflict can me merged

[GEEKYFOCUS]

Hi Maintainer.
I just resolved the conflict. Kindly review, so the issue can be closed

[GEEKYFOCUS]

Hi Maintainer, kindly review my PR and merge

[GEEKYFOCUS]

Hi Maintainer, kindly review my PR and merge, so i can get my point