Add supportfor projected Service Account token volumes

[scholzj]

Type of Change

• Enhancement / new feature

Description

This PR implements the SEP-155: Projected Service Account Tokens in Additional Volumes and adds support for projected service account tokens to additional volumes. It also adds documentation and system tests for using them for service account based authentication in Apache Kafka clients.

Checklist

• Update documentation
• Update CHANGELOG.md (if present)
• Write tests
• Make sure all tests pass
• Try your changes inside a Kubernetes cluster, not just from unit tests
• AI assistance was used to create this PR (see the Strimzi AI policy)

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.67%. Comparing base (0862411) to head (b995985).

Files with missing lines	Patch %	Lines
.../strimzi/operator/cluster/model/TemplateUtils.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13105      +/-   ##
============================================
+ Coverage     80.65%   80.67%   +0.01%     
- Complexity     6627     6634       +7     
============================================
  Files           344      344              
  Lines         22763    22773      +10     
  Branches       3116     3119       +3     
============================================
+ Hits          18359    18371      +12     
+ Misses         3183     3182       -1     
+ Partials       1221     1220       -1     

Files with missing lines	Coverage Δ
.../strimzi/operator/cluster/model/TemplateUtils.java	94.89% <90.00%> (+0.57%)	⬆️

... and 4 files with indirect coverage changes

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[scholzj]

/gha run pipeline=regression

[github-actions]

⏳ System test verification started: link

The following 6 job(s) will be executed:

• regression-brokers-and-security-amd64 (cncf-ubuntu-8-32-x86)
• regression-operators-amd64 (cncf-ubuntu-8-32-x86)
• regression-operands-amd64 (cncf-ubuntu-8-32-x86)
• regression-brokers-and-security-arm64 (cncf-ubuntu-8-32-arm)
• regression-operators-arm64 (cncf-ubuntu-8-32-arm)
• regression-operands-arm64 (cncf-ubuntu-8-32-arm)

Tests will start after successful build completion.

[github-actions]

🎉 System test verification passed: link