Add invoice creator whitelist

[Kingsman-99]

Label: complexity: high
Points: 200

Description

Open invoice creation allows any address to create invoices, which may not be appropriate for private platforms. This issue adds admin-controlled whitelist_creator() and remove_creator() functions — when the whitelist is non-empty, create_invoice() rejects any creator not on the list.

Technical Context

Involves lib.rs. Store whitelist as persistent key "creator_wl" holding Vec<Address>. Add whitelist_creator(env, address) and remove_creator(env, address) requiring admin auth. In create_invoice(), if whitelist is non-empty, assert creator is in the list.

Acceptance Criteria

• whitelist_creator() requires admin auth
• create_invoice() with non-whitelisted creator panics with "creator not whitelisted"
• Empty whitelist allows any creator (open mode)
• remove_creator() removes address from whitelist
• Test adds creator to whitelist, verifies non-whitelisted creator rejected
• All existing cargo tests pass
• cargo clippy passes with zero warnings

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[james2177]

@james2177 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer, i would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @james2177 to this issue.

[drips-wave]

Congratulations, @james2177! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @james2177: 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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