fix(asset-classes): Add carbon credit retirement tracking with immutable retirement records

[Kevin737866]

Description

Immutable retirement records preventing double-counting.

Acceptance Criteria

• retire_credits(owner, amount) permanently removes from circulation
• RetirementRecord: owner, amount, timestamp, purpose
• Retired excluded from total_supply; cannot unretire
• get_retirement_certificate(owner) returns all retirements
• Tests: retirement, history, retired credit transfer prevention

Files to Modify

• src/carbon_credit.rs
• src/rwa_token.rs

[emmyafolly123-coder]

@emmyafolly123-coder has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

fix(asset-classes): Add carbon credit retirement tracking with immutable retirement records
#175

ℹ️ Repo Maintainers: To accept this application, review their application or assign @emmyafolly123-coder to this issue.

[Paranoa-dev]

@Paranoa-dev has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would love to help tackle this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Paranoa-dev to this issue.

[ibochivincent-lang]

@ibochivincent-lang has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I’d like to work on Issue #175 because carbon credits need a definitive on-chain retirement mechanism that permanently removes retired units from circulation and prevents the same credits from being counted or transferred again.

I will first review src/carbon_credit.rs and src/rwa_token.rs, including the existing supply, balance, transfer, ownership, and storage patterns. I will also identify how asset-specific state is represented so retirement records integrate cleanly with the existing token architecture.

I will then implement retire_credits(owner, amount) with the appropriate authorization and balance checks. The function will permanently remove the specified quantity from the owner's circulating balance and ensure the retired amount is no longer included in the active total_supply.

Each retirement will create an immutable RetirementRecord containing the owner, retired amount, timestamp, and stated purpose. These records will be stored as an append-only history so previous retirements cannot be overwritten, removed, or reversed.

I will add get_retirement_certificate(owner) as a read-only query returning the owner's complete retirement history. The returned records will preserve their chronological order and provide sufficient information to independently verify the amount retired and its purpose.

The implementation will explicitly prevent unretirement. Once credits have been retired, they will no longer be part of the transferable supply, and the corresponding units cannot be restored through normal contract operations.

I will also update transfer/balance checks so retired credits cannot be transferred after retirement. The supply accounting will be kept consistent across retirement and transfer operations to prevent double-counting or creating a mismatch between balances and total supply.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @ibochivincent-lang to this issue.

[olalois]

@olalois has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer, I will love to be assigned this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @olalois to this issue.