Background jobs

[nilsandrey]

• The original requirements included "Introduce a periodic task to check drones battery levels and create history/audit event log for this".
• Described in WOI section of the wiki another job is designed to be included to provide a better experience checking the features of the API, with some very basic simulation of the behaviour of the drones to update dynamically the battery level changes, and the lastest part of the drone's state changes (delivering to delivered, returning, and then idle).

In the underlying infrastructure with Rails and Docker, a worker container should be created with a shell script, and running jobs implemented with RoR Active Jobs, Delayed Jobs, and Delayed Job Active Record.