feat(greenhousectl): validation of cluster name during onboarding

[kengou]

Description

• greenhousectl cluster boostrap enforces of the 40 character limit and no -- in the ClusterName
• the secret webhook is enforcing the name validation for type greenhouse.sap/kubeconfig. the func are re-used from cluster webhook:

  greenhouse/pkg/admission/cluster_webhook.go

  Lines 91 to 97 in 4ff77ed

  	if err := invalidateDoubleDashesInName(cluster, logger); err != nil {
  	return nil, err
  	}
  	// capping the name at 40 chars, so we ensure to get unique urls for exposed services per cluster. service-name/namespace hash needs to fit (max 63 chars)
  	if err := capName(cluster, logger, 40); err != nil {
  	return nil, err
  	}

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation Update
• 🎨 Style
• 🧑‍💻 Code Refactor
• 🔥 Performance Improvements
• ✅ Test
• 🤖 Build
• 🔁 CI
• 📦 Chore (Release)
• ⏩ Revert

Related Tickets & Documents

Added tests?

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help
• Separate ticket for tests # (issue/pr)

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

Added to documentation?

• 📜 README.md
• 🤝 Documentation pages updated
• 🙅 no documentation needed
• (if applicable) generated OpenAPI docs for CRD changes

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[IvoGoman]

Looks good.