v0.22.0

This release requires that you run migrations, as it converts all JSON columns
to JSONB. Call chancy.migrate() or use the CLI:

chancy --app <your app> misc migrate

• Chancy now starts some default plugins with reasonable defaults if they are
  not configured. This includes the Metrics, Leadership, Pruner,
  Recovery and WorkflowPlugin.
• Queue's now support a resume_at option, which allows them to automatically
  go active after the specified time. This can be used to implement circuit
  breakers.
• Added the convenience functions Chancy.pause_queue() and
  Chancy.resume_queue(). Calling this functions will emit queue.paused and
  queue.resumed events.
• Plugins must now provide a get_identifier() method, which should return a
  unique identifier for the plugin.
• Plugins may now implement get_depdenencies() to return a list of other
  plugins that they depend on.
• The default queue polling interval for new queues has been increased from
  1 to 5 seconds.
• All JSON columns have been converted to JSONB, which is more efficient and
  allows for indexing, and is supported by Django's JSONField type.

Metrics Plugin

• Internal implementation of the Metrics plugin has been significantly
  simplified.
• Metrics plugin now tracks job completion status on a per-queue basis as well
  as globally, which allows for the implementation of global, per-queue circuit
  breaker logic.

Django

• Chancy now comes with a Django app that gives you ORM and Admin access to
  Chancy's data. To install it, add chancy.contrib.django to your
  INSTALLED_APPS.
• The ProcessExecutor now has a django shim by default, simplifying setup.