feature(karmadactl): support split secret layout in init command

[tiansuo114]

What type of PR is this? /kind feature

What this PR does / why we need it: Part of #6670 Which issue(s) this PR fixes:

Fixes #6670

This commit introduces the capability for the karmadactl init command to deploy Karmada components using a split-style secret layout.

This change is part of a larger effort to refactor the certificate deployment mechanism within the karmadactl tool. It allows for a more granular and secure management of component certificates.

Special notes for your reviewer:

@chaosi-zju @zhzhuang-zju @XiShanYongYe-Chang

Does this PR introduce a user-facing change?:

`karmadactl`: Added the `--secret-layout` flag to the `init` command to support deploying with split certificate secrets.

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[gemini-code-assist[bot]]

Summary of Changes

Hello @tiansuo114, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant enhancement to the karmadactl init command by enabling a 'split' secret layout for Karmada component certificates. This change provides more granular and secure management of TLS materials, moving away from a single aggregated secret to individual secrets for each component. This refactoring improves the overall security posture and aligns with best practices for certificate handling in Kubernetes environments.

Highlights

• New --secret-layout Flag: The karmadactl init command now supports a new --secret-layout flag, allowing users to choose between legacy (single aggregated secret) or split (per-component TLS secrets) for certificate management. The default behavior remains legacy.
• Granular Certificate Management: When the split secret layout is selected, Karmada components will now utilize individual TLS secrets for various services such as the API server, aggregated API server, etcd, kube-controller-manager, and webhook. This enhances security by isolating certificate materials per component.
• Dynamic Deployment Configuration: The deployment logic for Karmada components has been updated to dynamically adjust command-line arguments, volume mounts, and volume definitions based on the chosen secret layout, ensuring proper certificate loading for both legacy and split modes.
• New Certificate Constants and Generation Logic: A new pkg/cert/constants.go file has been introduced to centralize secret and key names for the split layout. Additionally, new Go functions have been added to generate and manage these individual secrets, including a fresh service account key pair for the API server and kube-controller-manager.

Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/installation-cli.yaml

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Codecov Report

:x: Patch coverage is 65.94684% with 205 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 45.61%. Comparing base (04adc23) to head (ac24089). :warning: Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/karmadactl/cmdinit/kubernetes/deploy.go	45.62%	60 Missing and 27 partials :warning:
pkg/karmadactl/cmdinit/kubernetes/deployments.go	73.97%	55 Missing and 15 partials :warning:
pkg/karmadactl/cmdinit/kubernetes/command.go	0.00%	37 Missing :warning:
pkg/karmadactl/cmdinit/kubernetes/statefulset.go	91.79%	9 Missing and 2 partials :warning:
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6788      +/-   ##
==========================================
- Coverage   45.63%   45.61%   -0.03%     
==========================================
  Files         692      692              
  Lines       57580    58007     +427     
==========================================
+ Hits        26278    26457     +179     
- Misses      29662    29860     +198     
- Partials     1640     1690      +50     

Flag	Coverage Δ
unittests	45.61% <65.94%> (-0.03%)	:arrow_down:

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[tiansuo114]

The code passed CI/CD and works locally. I'm primarily interested in your feedback regarding scalability and design patterns. What is your opinion on the current architecture? @zhzhuang-zju