A wiki page as REQUIRED READING: whether somebody is asked to read it and mark so. 'edition' is the version to read — the approved edition in force where the page has one (see get_wiki_page_approval), else the one its lead last asked about; null when the page is asked of nobody. 'required' says whether it is asked of YOU and 'readAt' when you marked that edition (absent: not yet). 'readers' is the list as written: a person, 'members' (everybody on the project) or a team role. For the project's lead there is also 'people' — everybody the page is for today, each with 'askedAt', 'readAt' and 'remindedAt' for that edition, so who has NOT read it is whoever has no 'readAt' — and 'earlier', the marks on earlier editions. A mark is on an edition: a newer approved edition leaves the old marks in 'earlier' and asks everybody again.