feat(payment-distributor): implement two-step admin role rotation (transfer_admin/accept_admin) and authorization test suite

[chizzy192]

Context & Problem Statement

The payment-distributor contract in contracts/payment-distributor/src/lib.rs stores a single static admin initialized at contract deployment. Transferring contract ownership directly in a single step introduces high risk of permanent lockout if a typo or incorrect address is passed.

This issue implements a secure two-step admin ownership transfer pattern (transfer_admin proposes a PendingAdmin, and the new address must call accept_admin to finalize), accompanied by comprehensive negative authorization unit tests.

Architectural Motivation & Technical Requirements

• In contracts/payment-distributor/src/storage.rs:
  • Add StorageKey::PendingAdmin.
  • Add get_pending_admin, set_pending_admin, and clear_pending_admin storage helpers.
• In contracts/payment-distributor/src/lib.rs:
  • Implement transfer_admin(env, current_admin: Address, new_admin: Address):
    • Asserts current_admin.require_auth().
    • Writes new_admin to PendingAdmin.
  • Implement accept_admin(env, new_admin: Address):
    • Asserts new_admin.require_auth().
    • Validates new_admin == get_pending_admin().
    • Promotes new_admin to Admin, clears PendingAdmin, and emits AdminTransferred event.
• In contracts/payment-distributor/src/test.rs:
  • Test successful two-step transfer.
  • Test unauthorized caller on transfer_admin.
  • Test unauthorized caller on accept_admin.
  • Test chained transfers and event log emission.

Acceptance Criteria

• Two-step admin transfer fully implemented.
• AdminTransferred event emitted with previous and new admin addresses.
• All authorization failure branches assert Error::Unauthorized.
• cargo test -p payment-distributor passes cleanly.

Target Branch: dev
Estimated Effort: 5–12 hours | Delivery: 3–5 days
Difficulty: Medium

[Muyideen-js]

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

Hi, I can fix this

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[Stephan-Thomas]

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

hi, i would like to work on this.

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[Engr-Able]

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

Hello Maintainer, I’ve reviewed the requirements carefully and believe I can deliver a reliable solution that meets the specified acceptance criteria. I’d appreciate the opportunity to work on this issue.

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

[Sharon-alt29]

@Sharon-alt29 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer,

I've thoroughly read the context and problem statement section, and I can definitely handle this issue
Kindly assign me to it, thank you

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Sharon-alt29 to this issue.

[drips-wave]

Congratulations, @Stephan-Thomas! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @Stephan-Thomas: 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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[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @Stephan-Thomas as part of the Stellar Wave Program's 8th Wave 🥳

Moderator's reason: [Auto-assessed] The pull request is open with no maintainer response across any of the four channels, and the contribution is high quality, thoroughly implementing the two-step admin role rotation pattern, storage helpers, event emissions, and tests as requested in the issue.

😎 @Stephan-Thomas: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

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ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.