Provide ergonomic access to Pro features

[jonhoo]

Faktory now has a Pro edition, and that comes with (at the time of writing) two new API-facing features. Specifically, it adds unique jobs and expiring jobs. It'd be good to have a convenient interface to these without having to set fields in job.custom manually in the right format. These additional convenient methods should probably be under a non-default feature called "pro" so that non-pro users don't see methods they can't use.

[mperham]

The Faktory Pro OSX binary available with each release can be used to test it live if necessary (or at least prove it works once manually).

[jonhoo]

@mperham In line with https://github.com/contribsys/faktory/issues/180 I would love if the official client libraries did this in their CIs so other clients could copy their approach

[mperham]

Unfortunately I can't provide the Linux binary necessary for most CI environments.

[jonhoo]

@mperham that's fine -- a macOS-only CI test would be fine. Anything automated helps!

[worst]

@jonhoo are you actively working on this? I wanted to check before I start devoting some cycles to it. Expiring and unique jobs are relatively easy to get going I think.

[jonhoo]

I'm passively maintaining the project, but not actively working on this feature in particular, no. So please do feel free. I'm also looking for maintainers if anyone using Faktory on a regular basis is looking to step up to the plate :)

[rustworthy]

The JobBuilder PR followed by expiring and unique jobs PR will be the first steps in enabling ergonomic access to Enterprise Faktory features.

API for batch and trackable jobs will be added next.