[CT-17] Add input validation and transfer rules in multisig_transfer/rules.rs in opsce crate

[yusuftomilola]

Problem

contracts/multisig_transfer/src/rules.rs exists as a module but the validation logic is incomplete. Transfer amounts are not validated against min/max thresholds, and there are no checks for self-transfers or transfers to blocked addresses.

Proposed Solution

Create contracts/opsce/src/transfer_rules.rs. Implement a validate_transfer(env, from, to, asset_id, amount) guard function called at the start of every transfer execution.

Acceptance Criteria

• Returns Err(ContractError::SelfTransfer) if from == to
• Returns Err(ContractError::AmountBelowMinimum) if amount < min_transfer_amount
• Returns Err(ContractError::AmountAboveMaximum) if amount > max_transfer_amount
• Returns Err(ContractError::RecipientBlocked) if to is in a blocked addresses list
• set_transfer_limits(env, asset_id, min, max) configures limits (admin only)
• block_address(env, address) adds an address to the blocked list (admin only)
• Unit tests cover each validation rule and the happy path

[MooreTheAnalyst]

@MooreTheAnalyst has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hello! I’d love to take on this issue. I’ve reviewed the requirements and have a clear path forward for the implementation. I will add a validate_transfer guard in contracts/opsce/src/transfer_rules.rs to handle transfer validation before execution. The checks will cover self-transfers, minimum and maximum transfer limits, and blocked recipient addresses. I will also add admin-only functions for configuring transfer limits and managing blocked addresses, along with unit tests for each validation rule and the successful transfer flow. Could you please assign this to me?

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

[phertyameen]

@phertyameen has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi, I will like to work on this issue. I am a smart contract developer and
I have an eta of 12 hrs

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

[tolulopedd26]

@tolulopedd26 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Can i solve this issue?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @tolulopedd26 to this issue.

[drips-wave]

Congratulations, @phertyameen! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @phertyameen: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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