Enable configuration of result_ttl in django-rq-scheduler

[frbry]

Currently all scheduled and repeatable tasks are created with result_ttl=-1. This causes Result will never expire, clean up result key manually warnings to be logged, which can be annoying.

This PR creates a new field in BaseTask model so the user has the ability to change result_ttl value for newly created RQ tasks.

Note: result_ttl defaults to -1, which is weird because the RQ docs say it's 500 seconds by default: http://python-rq.org/docs/results/

[frbry]

Hi @g3rd, any chance you could take a look at this one? Thanks! :)

[frbry]

Hi @g3rd, any feedback?

[oudeismetis]

@frbry
Sorry for the slow reply on this.
At a high level this looks good. Going to pull this down and check it out, but I expect this will be merged soon.

Thanks for thinking of this!

[tom-price]

@oudeismetis, I've created PR #22 to merge @frbry's work into the project as there were minor issues related to the introduction of cron jobs.

[oudeismetis]

@frbry thank you again for the contribution!
Given the merge conflict, we are looking to merge #22 to bring this feature in.
Once that is merged I'll close this PR.

[frbry]

Thanks @oudeismetis and @tom-price!