Create a cron job.
name: The name of the job.
schedule: The job schedule.
username: The name of the user account under which to run the job command.
job-command: The job command.
--force: Overwrite an existing job of the same name.
--no-mail: Do not email the job output.
--home: A value for the HOME environment setting.
--path: A value for the PATH environment setting.
--shell: A value for the SHELL environment setting.
--check: Do not actually make any changes, but report whether or not a change would be made.