Add foreman_statistics plugin

[ezr-ondrej]

Packaging PRs (should get merged first):

• RPM: Add rubygem-foreman_statistics package foreman-packaging#5389
• DEB: Add foreman statistics plugin foreman-packaging#5391

[ekohl]

I'll let Travis finish, but otherwise 👍

[ekohl]

Oh, speaking of Travis, could you add a spec test like in https://github.com/theforeman/puppet-foreman/tree/master/spec/classes/plugin

[ezr-ondrej]

Oh, speaking of Travis, could you add a spec test like in https://github.com/theforeman/puppet-foreman/tree/master/spec/classes/plugin

Done :)

[ekohl]

Go Travis! Go! :)

[tbrisker]

This failure does not seem to be related:

1) Scenario: install foreman with journald Command "journalctl -u dynflow-sidekiq@orchestrator" stdout is expected to match /Everything ready for world: /

     Failure/Error: its(:stdout) { is_expected.to match(%r{Everything ready for world: }) }

       expected "-- Logs begin at Mon 2020-08-03 12:31:32 UTC, end at Mon 2020-08-03 12:42:36 UTC. --\nAug 03 12:36:5...:42:27 ubuntu1804-64.example.com foreman[4327]: Acquired orchestrator lock, entering active mode.\n" to match /Everything ready for world: /

[ekohl]

Correct, we've seen that every now and then. It happens when dynflow is too slow to start. https://projects.theforeman.org/issues/30275 is open and Adam started to look into it, but switching the autoloader to zeitwerk proved to be non-trivial. If you're interested in helping, theforeman/foreman#7843 is the current draft.