Implement Investor Participant Counter and Maximum Investor Cap

[Jayy4rl]

Description

Many regulatory frameworks limit the number of investors in a private securities offering (e.g., Regulation D in the US limits to 35 non-accredited investors, MiFID II in Europe has similar thresholds). The vault has no concept of investor count — anyone who passes KYC can deposit regardless of how many other investors already hold shares.

Requirements

• Add a DataKey::InvestorCount → u32 in instance storage
• Add a max_investors: u32 field to InitParams (0 = unlimited)
• Track unique investors: increment counter on first deposit (user_deposited == 0 before this deposit), decrement when a user fully redeems (all shares burned, balance == 0)
• In deposit and mint: if investor_count >= max_investors and this is a new investor, panic with Error::MaxInvestorsReached
• Add view functions: investor_count() -> u32, max_investors() -> u32
• Add set_max_investors(caller, max) -> () — admin-only
• Consider edge case: user A deposits, transfers all shares to user B (new investor), then A has 0 balance — should A be decremented? Yes, on next interaction or via a cleanup_investor_count function

Key Files

• lib.rs — deposit, mint, withdraw, redeem, redeem_at_maturity, transfer
• storage.rs — new keys
• types.rs — InitParams new field
• errors.rs — new MaxInvestorsReached variant

Definition of Done

• Investor count tracks unique share holders
• Max investor cap enforced on new deposits
• Count decrements when users fully exit
• Admin can update the cap
• Tests cover: cap enforcement, re-entry after exit, transfer impact on count

[Nanle-code]

@Nanle-code has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Let me work on this

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

[drips-wave]

Congratulations, @Nanle-code! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @Nanle-code: 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.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊