Use job payload instead of worker instance in middleware

[tony-pizza]

I'm proposing that we drive the Sidekiq middleware off of the job payload hash instead of the worker instance.

Why?

There are many ways to configure job options on a Sidekiq worker (See sidekiq/sidekiq#6092 (comment)):

Sidekiq.default_job_options
sidekiq_options key: value
JobClass.set(key: value)
PeriodicManager.register(..., key: value)

Sidekiq merges all of these options into one payload that gets passed into middleware (as the second argument of call()).

In the current middleware, job options are mostly fetched via worker.class.sidekiq_options, which would only look at options set via sidekiq_options in the worker class and ignore any options set via other methods (e.g. periodic job config). Addressing this by fetching options from various places (as is done in periodic_job_key()) adds unnecessary work and complexity as Sidekiq already merges options from various sources into the job payload.

What?

• Refactors the internals of the Sidekiq server middleware to use the job payload hash instead of the worker instance
• Updates specs accordingly

[tony-pizza]

No need for this at all anymore :)

[tony-pizza]

I removed this as usage outside of Rails would have led to bugs. We can expect job_payload to always have string keys.

[tony-pizza]

Also, I'm pretty sure periodic_job.options.fetch() would raise an error anyway. Same issue as #31