Add rake task to clean DB

lib/tasks/crono_tasks.rake

@@ -0,0 +1,9 @@
+namespace :crono do
+  desc 'Clean unused job stats from DB'
+  task clean: :environment do
+    Crono.scheduler = Crono::Scheduler.new
+    require File.join(Rails.root, 'config', 'cronotab')
+    current_job_ids = Crono.scheduler.jobs.map(&:job_id)
+    Crono::CronoJob.where.not(job_id: current_job_ids).destroy_all
+  end
+end