Amendment XLS: Closed-ended vault

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A closed-ended vault is a fixed-term fund. Unlike an open-ended vault, where depositors can come and go at any time, a closed-ended vault has a defined lifecycle: it collects capital for a limited period, puts that capital to work for a fixed term, and then winds down and returns the proceeds to depositors. Once the fund is under way, no new money can join and existing money cannot leave until the term ends. This gives the operator a stable, known amount of capital to deploy and gives depositors a clear, up-front understanding of when their funds are committed and when they will be returned.

A closed-ended vault moves through three stages in order, and never goes backwards:

• Subscription — the fund-raising window. Depositors put capital in, and may change their mind and withdraw while the window is open. The size of the fund is still settling during this stage.
• Investment — the lock-up. The subscription window has closed, the amount of capital is now fixed, and it is deployed into loans. Deposits and withdrawals are both suspended so the capital stays in place for the whole term.
• Redemption — the wind-down. Loans have matured and been repaid, no new lending takes place, and depositors withdraw their share of the returned capital.

The move from one stage to the next happens automatically at pre-set dates that are chosen when the vault is created and cannot be changed afterwards. Because the schedule is fixed and public, everyone involved knows in advance when the fund-raising window closes, how long their capital is committed, and when they can expect to be repaid.

Spec: #587