Channel, Subscription, Video, SearchFind, ExploredChannel and BlockedChannel (and LIVE_OR_UPCOMING)
leave app/models.py for app/catalog/models.py; app.tables registers them. The User↔Subscription
relationship names its other side as a type only. No schema change.
channels.list simply omits a terminated channel, so nothing was stamped and the
channel page spent a quota unit on it every time. The miss is stamped like a
fetch; the published_at sentinel that kept it stale is gone.
Channel metadata (banner, avatar, description, counts) was fetched only the first time a
channel was seen: the subscription import asked only for channels with no details, and the
channel page only for ones missing a join date. 394 of 397 subscribed channels had July
metadata. Both now also refresh details older than DETAILS_MAX_AGE (7 days), through one
shared staleness rule; channels.list costs 1 unit per 50 channels.
peter