Add Credential Dispute Resolution System (#985)

[maztah1]

Summary

Implements a complete credential dispute resolution system that allows stakeholders to flag and contest fraudulent credentials (e.g., fake university degrees).

Changes Implemented

Core Functionality

• dispute_credential() - Allows any address to initiate a dispute against a credential with evidence
• resolve_dispute() - Admin-only function to resolve disputes (upheld or dismissed)
• get_credential_disputes() - Retrieves all disputes associated with a credential
• get_credential_status() - Returns the current status of a credential

Data Structures

• CredentialStatus enum: Valid, Disputed, Rejected
• DisputeResolution enum: Upheld (credential rejected), Dismissed (credential remains valid)
• CredentialDispute struct: Tracks dispute details including initiator, reason, evidence hash, timestamps, and resolution
• Event types: DisputeInitiatedEventData and DisputeResolvedEventData

Storage and State Management

• Updated Credential struct to include status field (defaults to Valid)
• Added DataKey entries: CredentialDisputes, CredentialDisputeEntry, CredentialDisputeCount
• Added ActivityType entries: DisputeInitiated, DisputeResolved

Workflow

1. Any address can call dispute_credential() with reason and evidence hash
2. Credential status changes from Valid to Disputed
3. Admin reviews evidence and calls resolve_dispute()
4. If upheld: credential status becomes Rejected
5. If dismissed: credential status returns to Valid
6. Multiple disputes can be filed against same credential (after resolution)

Testing

Comprehensive test suite includes:

• Successful dispute initiation
• Preventing disputes on already-disputed credentials
• Error handling for non-existent credentials
• Resolving disputes as upheld (rejection)
• Resolving disputes as dismissed (remains valid)
• Access control (admin-only resolution)
• Multiple disputes on same credential lifecycle
• Empty disputes list handling
• Event emission verification

Technical Details

• Follows existing codebase patterns and conventions
• Uses existing TTL constants (STANDARD_TTL, EXTENDED_TTL)
• Integrates with activity recording system
• Emits events for audit trail
• Proper authorization checks on all functions

Estimated Time

3 hours (as specified in issue QuorumProof#985)

Related Issue

Closes QuorumProof#985

Checklist

• Add CredentialStatus enum (Valid, Disputed, Rejected)
• Implement dispute_credential() - any address can initiate
• Implement resolve_dispute() - admin-only
• Implement get_credential_disputes()
• Add comprehensive tests for dispute flow
• Update Credential struct with status field
• Add proper event emission
• Integrate with activity tracking