[Heartbeat] Adds maintenance windows !!

[shahzad31]

Proposed commit message

Added maintenance windows in heartbeat in RFC 5545 format using rrule-go library, this makes it compatible with kibana alerting maintenance windows which are using the same format https://www.elastic.co/guide/en/kibana/current/maintenance-windows.html

This will allow us to simple pass values from alerting maintenance windows where those are applicable to synthetics monitors as heartbeat configs

example being

heartbeat.monitors:

- type: http
  id: my-monitor
  urls: ["http://localhost:9200"]
  maintenance_windows:
    - freq: daily
      dtstart: "2024-11-04T01:00:00.000Z"
      interval: 1
      byweekday: [MO, TU, WE, TH, FR]
      duration: 3600000

Limitations

• Only Daily, weekly, Monthly and Yearly Frequencies are allowed.
• If DTStart is older than 2 years, it will throw error.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

Author's Checklist

• [ ]

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[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @shahzad31? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/obs-ds-hosted-services (Team:obs-ds-hosted-services)

[cmacknz]

Approving go.mod changes.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b maintenance-windows upstream/maintenance-windows
git merge upstream/main
git push upstream maintenance-windows

[emilioalvap]

LGTM with suggestions 🚀

[emilioalvap]

/test

[shahzad31]

/test