This code empirically doesn't work. It's not entirely clear why, even
having done quite a bit of debugging; partly because the code is quite
convoluted, and because it shows the symptoms of people making changes
over time without really understanding how it was supposed to work.
Moreover, this code targets an old version of the APNs provider API.
Apple deprecated that in 2015, in favor of a shiny new one which uses
HTTP/2 to meet the same needs for concurrency and scale that the old
one had to do a bunch of ad-hoc protocol design for.
So, rip this code out. We'll build a pathway to the new API from
scratch; it's not that complicated.
We'd been getting errors from APNs that appeared to say that the
device tokens we were trying to send to were invalid. It turned out
that the device tokens didn't match the "topic" (i.e. app ID) we were
sending, which was because the topic was wrong, which was because we
were using the wrong SSL cert. But for a while we thought it might be
that we were somehow messing up the device tokens we put into the
database. This logging helped us work out that wasn't the issue, and
would have helped our debugging sooner.
Now this function will delete tokens from RemotePushDeviceToken if it
is running on notification bouncer or PushDeviceToken if it is running
on a server which doesn't use notification bouncer.
This is an incomplete cleaned-up continuation of Lisa Neigut's push
notification bouncer work. It supports registration and
deregistration of individual push tokens with a central push
notification bouncer server.
It still is missing a few things before we can complete this effort:
* A registration form for server admins to configure their server for
this service, with tests.
* Code (and tests) for actually bouncing the notifications.
This completes the process of simplifying the interface of the
send_*_push_notification functions, so that they can effectively
support a push notification forwarding workflow.
This refactoring is preparation for being able to forward push
notifications to users on behalf of another Zulip server.
The goal is to remove access to the current server's database from the
send_*_push_notification code paths.