Add support for ietf-schedule basic recurrence

[saba8814]

Description

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe):

[mattiaswal]

Also add the the "magic" key word fix #issue number in the PR description, this closes the open issue automatically when merged.

[saba8814]

Also add the the "magic" key word fix #issue number in the PR description, this closes the open issue automatically when merged.

Thing is #1301 is formulated in way that it is support for full unattended upgrade, and this PR adds scheduling stuff and just a check for update availiability thus I ommited it from git message, since full implementation of unnattended-upgrade will be handled in a separete merge request.

[troglobit]

Still haven't had the time to fully look at this, but a few general pointers that are useful:

1. Personally I prefer to use "Add support for" instead of "feat:", it feels more human and invites to a discussion
2. Each PR should have a description which introduces the reviewer to the topic, nothing too in-depth, just a summary of the why:s and what:s to expect. Screenshots is a favorite! This is also a good place to bring up limitations (for example: "most of the advanced features are deviated to allow for a simple good-enough first release", future work, etc.

I hope to have some time tomorrow for a detailed look at the changes 😃