Replace parse-cron with fugit

[adamruzicka]

parse-cron seems to be unmaintained since 2016, fugit seems to be still active. In addition to that, it should also allow expressing intervals such as "first Monday each month" which wasn't possible with parse-cron.

TODO:

• packaging

[ekohl]

Dependency should be available: theforeman/foreman-packaging#9208. I suspect packit fails because fugit is not listed as a BuildRequires, but we can't deal with that on EL8. For EL9 we may have theforeman/foreman-packaging#8414, but for now we'll have to accept the limitation.

@evgeni perhaps we can patch the spec file based on the gem by autoregenerating the deps, similar to what we do in bump_rpm.sh.

[evgeni]

@ekohl we certainly can (and packit has a hook for that), just nobody sat down and did innocent whistle

[adamruzicka]

Thank you @ekohl !

[sjha4]

I am seeing some change in behavior with fugit.

[1] pry(main)> require 'fugit'
=> false
[2] pry(main)> @parser ||= Fugit.parse_cron('* * * * abc')
=> nil
[3] pry(main)> @parser ||= Fugit.parse_cron(nil)
=> nil
[4] pry(main)> @parser ||= Fugit.parse_cron('* * * * *')
=> #<Fugit::Cron:0x000056255ad0a590 @cron_s=nil, @day_and=nil, @hours=nil, @minutes=nil, @monthdays=nil, @months=nil, @original="* * * * *", @seconds=[0], @timezone=nil, @weekdays=nil, @zone=nil>

What that does is have nil failures in next_occurrence_time method. Here is the workflow that raises that..

[5] pry(main)> recurring_logic = ::ForemanTasks::RecurringLogic.new_from_cronline('* * * * abc')
=> #<ForemanTasks::RecurringLogic:0x000056255ac31fb0 id: nil, cron_line: "* * * * abc", end_time: nil, max_iteration: nil, iteration: 0, task_group_id: nil, state: nil, triggering_id: nil, purpose: nil>
[6] pry(main)> recurring_logic.valid_cronline?
NoMethodError: undefined method `previous_time' for nil:NilClass
from /home/vagrant/foreman/.vendor/ruby/2.7.0/gems/foreman-tasks-8.0.0/app/models/foreman_tasks/recurring_logic.rb:101:in `next_occurrence_time'

[sjha4]

Please see: #717 and let me know if that makes sense.