task(ipfs): implement credential upload service

[a-malik-gh]

Module

ipfs

Background & context

OpenCred stores credential documents on IPFS to ensure decentralized and tamper-resistant storage.

This task introduces the first IPFS integration layer for uploading credential JSON payloads and retrieving their content identifiers (CIDs).

The implementation should be modular because future services and blockchain verification flows will depend on it.

Acceptance criteria

• An IPFS upload service is implemented
• JSON credential payloads can be uploaded successfully
• The returned CID is exposed to calling services
• Errors are handled gracefully
• Environment variables support configurable IPFS gateways/providers
• Unit tests cover successful uploads and failure scenarios
• README documentation explains local configuration

Files to edit

• src/ipfs/ipfs.service.ts
• src/ipfs/ipfs.module.ts
• .env.example
• README.md

Helpful resources

• IPFS Docs:
  https://docs.ipfs.tech/

• Helia IPFS:
  https://github.com/ipfs/helia

Estimated difficulty

Medium — some domain knowledge required