feat: implement credential controller and routes

[tech-adrian]

Credential Controller & Routes Implementation

Closes #8

Overview

Implements credential management endpoints for certificates and achievements as specified in issue #8.

Changes Made

New Files

• src/controllers/credential.controller.ts - Controller with three main endpoints
• src/routes/v1/credentials.routes.ts - Route definitions with validation
• tests/unit/credential.controller.test.ts - Comprehensive unit tests (14 tests, all passing)

Modified Files

• src/routes/index.ts - Added credentials routes to API

Implemented Endpoints

1. GET /api/v1/credentials

• Auth: Required
• Purpose: Retrieve all credentials for authenticated user
• Query Params: moduleId, fromDate, toDate, page, limit
• Features:
  • Pagination support (default: page=1, limit=10, max=100)
  • Filter by module
  • Filter by date range
  • Returns credential details with module information
  • Includes shareable verification links

2. GET /api/v1/credentials/:id

• Auth: Required (user must own credential)
• Purpose: Retrieve single credential details
• Features:
  • Full credential information
  • Module details (title, description, category, difficulty, reward)
  • Holder information
  • Verification metadata
  • Shareable link

3. GET /api/v1/credentials/verify/:onChainId

• Auth: Not required (public endpoint)
• Purpose: Public verification of credentials
• Features:
  • Verifies by onChainId or regular credential ID
  • Returns validation status
  • Shows credential holder and module information
  • Timestamp of verification

Technical Details

Validation

• Uses Zod schemas for input validation
• UUID validation for IDs
• ISO 8601 datetime validation for date filters
• Numeric validation for pagination parameters

Error Handling

• Proper HTTP status codes (400, 401, 404)
• Descriptive error messages
• Uses custom error classes (BadRequestError, NotFoundError, UnauthorizedError)
• Wrapped with asyncHandler for promise rejection handling

Database

• Uses Prisma ORM
• Efficient queries with proper includes
• Pagination with count queries
• Indexed lookups by ID and onChainId

Testing

• 14 unit tests covering all endpoints
• Tests for success cases
• Tests for error cases (invalid input, unauthorized access, not found)
• Tests for filtering and pagination
• All tests passing ✅

Acceptance Criteria Met

• ✅ Users can view all their earned credentials
• ✅ Public verification endpoint returns credential validity
• ✅ Verification works without authentication
• ✅ Credential details include on-chain reference
• ✅ Filtering and pagination work correctly
• ✅ Unit tests written and passing

Code Quality

• ✅ Linting passed
• ✅ All existing tests still passing (225 tests total)
• ✅ Follows existing codebase patterns
• ✅ Proper TypeScript types
• ✅ Comprehensive error handling
• ✅ Clean, readable code with comments

[tech-adrian]

@3m1n3nc3 please review and merge