Implement subscription credit system and account balance

[Smartdevs17]

Implement subscription credit system and account balance

Description

Context: Subscribers may have account credits from refunds, promotions, or overpayments that should apply to future charges.

Current Limitation: No credit balance system exists.

Expected Outcome: Implement credit system with balance tracking and automatic application.

Acceptance Criteria

• Implement AccountCredit: balance, transactions[], expiration_policy
• Add credit issuance (manual and automatic)
• Implement automatic credit application on charging
• Support credit transfer between accounts
• Add credit expiration handling
• Implement credit transaction history
• Create React Native credit management UI
• Write tests for credit operations

Technical Scope

Files Likely Affected:

• contracts/credit/src/lib.rs - New credit module
• app/stores/creditStore.ts - Credit state
• app/screens/CreditBalanceScreen.tsx

APIs/Contracts Involved:

• issue_credit(subscriber: Address, amount: i128, reason: String)
• apply_credit(subscription_id: SubscriptionId) -> CreditApplied
• get_credit_balance(subscriber: Address) -> i128

Edge Cases to Consider:

• Credit expiration
• Negative balance

[olaayoade91-byte]

@olaayoade91-byte has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

HELLO I WOULD LIKE TO WORK ON THIS

ℹ️ Repo Maintainers: To accept this application, review their application or assign @olaayoade91-byte to this issue.