Support the deploy freeze windows

[noahingh]

Sometimes users want to prevent deployments for a particular period, for example, during a planned vacation period when most employees are out. This feature makes the deployment much safety.

Implement

Gitploy gets the last time matched with the crontab expression and verifies the current time is in duration from the start time. I need to get the last time matched with the start pattern to implement. But there is no package support getting the last time (e.g. robfig/cron), so we decide to make a new package.

Example

envs:
  - name: production
    frozen_windows:
      # Freeze every midnight
      - start: "55 23 * * *"
        duration: "10m"
        location: "Asia/Seoul"
      # Freeze weekend 
      - start: "* * * * 5,6"
        duration: "1m"
        location: "Asia/Seoul"

[noahingh]

I've made a new package gitploy-io/cronexpr, now I can provide a new feature called deploy freeze window.