This commit migrates the Subscription's notification fields from a
BooleanField to a NullBooleanField where a value of None means to
inherit the value from user's profile.
Also includes a migrations to set the corresponding settings to None
if they match the user profile's values. This migration helps us in
getting rid of the weird "Apply to all" widget that we offered on
subscription settings page.
The mobile apps can't handle None appearing as the stream-level
notification settings, so for backwards-compatibility we arrange to
only send True/False to the mobile apps by applying those defaults
server-side. We introduce a notification_settings_null value within a
client_capabilities structure that newer versions of the mobile apps
can use to request the new model.
This mobile compatibility code is pretty effectively tested by the
existing test_events tests for the subscriptions subsystem.
Namely, annotate as best as possible, and add notes to indicate preference,
if QuerySet develops generic typing.
Note that the return values of functions with annotations changed in this
commit are used elsewhere as QuerySets, so the Sequence[T] approach used
for some functions in models.py is not applicable.
We extract get_bulk_stream_subscriber_info() from this
function to remove some of the complexity. Also, in that
new function we avoid a hop to the database by querying
on stream ids instead of recipient ids. The query that
gets changed here does require a join to the recipient
table (to get the stream id), so it's a little bit of a
tradeoff.
The first method we extract to this library is
get_active_subscriptions_for_stream_id().
We also move num_subscribers_for_stream_id() to here, which
is slightly annoying (having the method on Stream was nice)
but avoids some circular dependency issues.
Harshit Bansal
neiljp (Neil Pilgrim)
rht
Steve Howell