[Medium] Implement credential revocation system

[Josie123-Dev]

Task Description

Create credential revocation system:

• Revoke individual credentials
• Bulk revoke credentials
• Maintain revocation list
• Check revocation status
• Implement revocation reasons

Requirements

• Add revocation status to credentials
• Implement revocation endpoint
• Create revocation registry
• Check revocation before use
• Track revocation reasons

Acceptance Criteria

• Individual revocation works
• Bulk revocation works
• Revocation list is maintained
• Revocation status is checked
• Reasons are tracked

[thebabalola]

Hi maintainer. I'm a technical Stellar engineer specializing in secure identity and data systems. I see the requirement to implement a credential revocation system. For this, I will architect a highly-available revocation registry, likely leveraging a caching layer (Redis) for fast lookups backed by PostgreSQL. The endpoint will handle revocation status checks in O(1) time to ensure we don't block the critical path of verification. Ready to dive in once assigned.

[grantfox-oss]

🦊 GrantFox — @thebabalola has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #23)
2. Your PR will be reviewed by the GuardZero144 maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@thebabalola's PR #139 was approved and merged by @Josie123-Dev.

🏆 @thebabalola: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (974 total points). Track your full progress on GrantFox.

👏 Great work, @thebabalola! Keep contributing to GuardZero144.