The goal here is to make all our peer_data functions
basically work in id space. Passing a full `sub`
to these functions is a legacy of when subscriber
info was attached to a full stream "sub" object,
but we don't care about anything sub-related
(color, description, name, etc.) when we are
dealing with subscriptions.
When callers pass in stream_id, you can be more
confident in a quick skim of the code that we're
not mutating anything in the "sub".
This de-clutters stream_data a bit. Since our
peer data is our biggest performance concern,
I want to contain any optimizations to a fairly
well-focused module.
The name `peer_data` is a bit of a compromise,
since we already have `subs.js` and we use
`sub` as a variable name for stream records
throughout our code, but it's consistent with
our event nomenclature (peer/add, peer/remove)
and it's short while still being fairly easy
to find with grep.
This sets us up to use better system-wide data structures
for tracking subscribers.
Basically, instead of storing subscriber data on the
"sub" objects in stream_data.js, we instead have a
parallel data structure called stream_subscribers.
We also have stream_create, stream_edit, and friends
use helper functions rather than accessing
sub.subscribers directly.
Since the denmark stream stub has subscribed = true,
we include the current user id in it's subscribers set.
We remove user `me` from sweden stream stub for the same
reason.
This fixes the regression introduced in the pervious
commit to regain the 100% line coverage in `user_pill.js`
as well as `stream_pill.js`.
The new `stream_edit.js` mainly tests for:
* The stream related queries of the typeahead in `user_pill.js`
* The "Add subscribers" event handlers.
* The event handler which displays the settings for a stream.
