Add automatic background job runs to Docker containers

[pglombardo]

The application can preemptively expire and clean up pushes. This is done daily on pwpush.com in a hacky automated fashion.

The two tasks are (run from the command line):

1. rake daily_expiration
2. rake delete_expired_and_anonymous

We can add the automated run of these tasks by adding cron to the Docker containers and using the whenever gem to schedule the daily task.

[ivancarlosti]

A kindly reminder or workaround to have it ;)

[pglombardo]

I've started this 3 times before getting interrupted every time. :-)

I will get to this soon. In the meantime, you can run the tasks as cron jobs:

[pglombardo]

#2601 is in progress. This will add a new Docker container dedicated at running background tasks. Thanks for the nudge!

[pglombardo]

The pwpush-worker docker container image is out (quietly). Once it stabilizes, get enough feedback and write documentation I'll make a larger announcement.

tldr on how to run: just run with the same environment as the pwpush container. It will automatically run periodic background jobs. A dashboard to view executions is in progress in #2638

https://hub.docker.com/r/pglombardo/pwpush-worker/tags