团队成员资格：数据、权限和操作
防止最后一位所有者离开，要求两步所有权转移，离开时撤销会话和令牌，并为每次成员变更写入审计记录。
Comments attach to a document revision, support hide versus delete, allow mentions only of users the commenter can see, bound the edit window, and record moderation actions in an audit trail.