Add krel validate cmd

[npolshakova]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Introduces new krel validate <release-notes-maps> command for release notes team to use when checking for invalid formatting.

The release notes team is blocked whenever invalid yaml is merged into sig-release:

kubernetes/sig-release#2589
kubernetes/sig-release#2541

Invalid yaml can be introduced during the review process when people apply changes or manually edit the maps (not through krel, but in an editor).

Examples of runs:

Valid check:

krel validate sig-release/releases/release-1.30/release-notes/maps
...
Validating YAML file: sig-release/releases/release-1.30/release-notes/maps/pr-123935-map.yaml
File sig-release/releases/release-1.30/release-notes/maps/pr-123935-map.yaml is valid YAML.
YAML file sig-release/releases/release-1.30/release-notes/maps/pr-123935-map.yaml is valid.
Validating YAML file: sig-release/releases/release-1.30/release-notes/maps/pr-124001-map.yaml
File sig-release/releases/release-1.30/release-notes/maps/pr-124001-map.yaml is valid YAML.
YAML file sig-release/releases/release-1.30/release-notes/maps/pr-124001-map.yaml is valid.
All release notes are valid.

Invalid yaml:

Validating YAML file: sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml
FATA failed to validate release notes: YAML validation failed for sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml: YAML unmarshal failed for sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml:error converting YAML to JSON: yaml: line 3: found character that cannot start any token 

Which issue(s) this PR fixes:

Catches occurrences of #2753

Special notes for your reviewer:

Eventually, this command can be added to release-actions and run as a workflow similar to kubernetes/sig-release#2547.

Does this PR introduce a user-facing change?

Introduced new `krel validate` command for validating committed release note edits. 

[npolshakova]

@satyampsoni this can be used to validate the yamls instead of relying on the script. We can move this to a GitHub action once it goes in.

[npolshakova]

@kubernetes/sig-release-leads @xmudrii Can you give this another pass when you have a chance? Thanks!

[cpanato]

/lgtm

but i will elave for @xmudrii for final review

/hold

[xmudrii]

Just a few questions and nits, otherwise LGTM :)

Sorry for the delay!

[npolshakova]

Just a few questions and nits, otherwise LGTM :)

Sorry for the delay!

Thanks @xmudrii for the review! Here's the updated behavior with the cmd flag:

If it's not provided:

❯ go run cmd/krel/main.go release-notes validate 
FATA path to release notes must be provided via --path-to-release-notes 
exit status 1

If it's provided:

❯ go run cmd/krel/main.go release-notes validate --path-to-release-notes ~/kubernetes/sig-release/releases/release-1.30/release-notes
Validating YAML file: /Users/ninapolshakova/kubernetes/sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml
FATA validating release notes: validating YAML file /Users/ninapolshakova/kubernetes/sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml: punctuation check for file /Users/ninapolshakova/kubernetes/sig-release/releases/release-1.30/release-notes/maps/pr-112957-map.yaml: the 'text' field does not end with valid punctuation: '"kubelet allowed specifying a custom root directory for pod logs (instead of the default /var/log/pods) using the `podLogsDir` key in kubelet configuration."
' 
exit status 1

Then the top level krel help message:

❯ go run cmd/krel/main.go 
Usage:
  krel release-notes [flags]
  krel release-notes [command]

Available Commands:
  validate    The subcommand for validating release notes for the Release Notes subteam of SIG Release

[xmudrii]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, npolshakova, xmudrii

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• cmd/krel/OWNERS [cpanato,xmudrii]

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[xmudrii]

/hold cancel