Implement Contract metadata CRUD API

Description

Implement robust CRUD for escrow contract metadata records.

Requirements and context

• Must be secure, tested, and documented
• Should be efficient and easy to review
• Repository scope: Talenttrust/Talenttrust-Backend only
• Keep implementation aligned with existing project architecture and coding standards

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/backend-03-contract-metadata-crud-api
• Implement changes
  • Write code in: src/index.ts and modularized src/* files for implement robust crud for escrow contract metadata records.
  • Write comprehensive tests: src/**/*.test.ts with integration and unit suites
  • Add documentation: README.md and docs/backend/
  • Include NatSpec-style comments where applicable (or equivalent structured doc comments)
  • Validate security assumptions and threat scenarios

Test and commit

• Run tests
• Cover edge cases and failure paths
• Include test output and security notes

Example commit message

feat: implement contract metadata crud api with tests and docs

Guidelines

• Minimum 95 percent test coverage for impacted modules
• Clear documentation with reviewer-focused structure
• Timeframe: 96 hours