Instead of treating false differently from undefined, our
function is now a regular boolean function, and we limit our
code comments to the one corner case where the true/false
decision is kind of arbitrary and possibly confusing.
In stream settings, if user add subscriber to unsubscribed public
stream from `Add` input widget it gives lots of blueslip warnings,
cause user isn't subscribed to public stream.
Fix this by changing condition to `sub.can_access_subscriber` from
`sub.subscribed` in blueslip warning, cause user can access
subscribers in such cases even if not subscribed to stream.
Tweaked by tabbott to make the node tests pass.
Using stream_id in recipient comparisons fixes a
bug in this scenario: go to home view, send message
to stream, wait for admin to rename stream, send
another message to the stream. Before this change,
the stream name would live-update but you'd get a
spurious recipient bar due to the prior message still
having the old stream name in places internally.
There were other ways to fix the live-update glitch,
but it's just generally cleaner to do stream id
comparisons.
Part of this change is to add stream_id to
compose_fade.set_focused_recipient().
