Since there is little point in retrying so often when a service is down
or does not exist anymore. Subscriptions are renewed 1 day before they
should expire, so retrying in 30 minutes, then 2 hours, then 12 hours
is fine. If even after that, the remote server does not work, there is
little sense in retrying more often than once a day

Also, uniqueness of the job should ensure that failed retries will
not result in multiple retries for the same endpoint when the next
resubscription cycle comes

* Fix Scheduler::SubscriptionsScheduler, add worker test for it

* Change production log level of Sidekiq to "warn" instead of "info"

* Fix #2473 - Use sidekiq scheduler to refresh PuSH subscriptions instead of cron

Fix an issue where / in domain would raise exception in TagManager#normalize_domain

PuSH subscriptions refresh done in a round-robin way to avoid hammering a single
server's hub in sequence. Correct handling of failures/retries through Sidekiq (see
also #2613). Optimize Account#with_followers scope. Also, since subscriptions
are now delegated to Sidekiq jobs, an uncaught exception will not stop the entire
refreshing operation halfway through

Fix #2702 - Correct user agent header on outgoing http requests

* Add test for SubscribeService

* Extract #expiring_accounts into method

* Make mastodon:push:refresh no-op

* Queues are now defined in sidekiq.yml

* Queues are now in sidekiq.yml