Avoid forcing applications to have a root ApplicationJob defined

[alxckn]

While trying out mission control in an existing application, I encountered some errors whose origin is the fact that there is no root ApplicationJob.

Mission control defines its own MissionControl::Jobs::ApplicationJob, however it doesn't seem to be used due to how each files' class is defined:

module MissionControl::Jobs::FailedJobsBulkOperations
  def bulk_limited_filtered_failed_jobs
      ApplicationJob.jobs # would work with MissionControl::Jobs::FailedJobsBulkOperations::ApplicationJob or ::ApplicationJob
    end
end

This is a proposal to use ActiveJob::Base in application code instead so it is compatible with applications that don't have a root ApplicationJob. Furthermore, this removes the unused MissionControl::Jobs::ApplicationJob.

[rosa]

Sounds good, thanks @alxckn! I think I'm going to take this a bit further and replace ActiveJob::Base.jobs with ActiveJob.jobs, to be consistent everywhere.