This will be a singleton that will query the model for all scheduled or pending swarming tasks. It will provide an Enqueue method, and a stub for the pubsub endpoint to callback.

Refer to the doc for full spec
https://docs.google.com/a/google.com/document/d/10viQ0-7zOSHyVzWB9YCcAW1pVl_ywBleP7Yc-_pEAa8/edit?usp=sharing