[WIP] Improve cron validation function, cron helpers and cron input errors

[peaklabs-dev]

Changes:

TODO:

• Fix: yearly is not a valid CRON expression or any custom expression error internally
• Fix: cron Input for application/ services when edit seems to have no validation
• Improve all helpers for corn inputs (backup, cron job, auto update, update check, server cleanup)
• Improve error dispatches for cron inputs (backup, cron job, auto update, update check, server cleanup)
• Improve validation function for cron inputs -> use the right function!
• Improve cron validation function generally
• Fix: 11 18 *** this is invalid -> because of missing spaces.
• Feat: cron auto formatting -> automatically add spaces between cron (fixes the error for 11 18 ***)
• Feat: add more default crons?
• Feat: New improve docs (new PR on docs)