【数据存储】邮件附件的托管存储：附件与正文分离

---发送邮件：正文入库，附件独立登记
function Mail.sendWithAttach(toId, title, memo, items)
    local mailId = Mail.insertBody(toId, title, memo)
    if items and #items > 0 then
        for _, it in ipairs(items) do
            AttachRepo.deposit(mailId, it)
        end
    end
    return mailId
end

---附件托管：物品转托管对象
function AttachRepo.deposit(mailId, item)
    attachRepo[#attachRepo + 1] = {
        mailId = mailId, item = item.id, n = item.n,
        bind = item.bind, state = "holding",
    }
end

function AttachRepo.claim(attachId, actor)
    local rec = attachRepo[attachId]
    if rec.state ~= "holding" then return false, "附件已领取" end
    if not actor:HasBagBlank() then return false, "背包已满" end
    rec.state = "claimed"
    giveitem(actor, rec.item, rec.n, rec.bind, "邮件附件")
    QF_LogAttach(attachId, actor:GetUserId(), rec.item)
    return true
end