[documentation] Secrets management in Operator 1.11+ (#1555)

[tbavelier]

What does this PR do?

• Cherry-picks [documentation] Secrets management in Operator 1.11+ #1555

Motivation

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Additional Notes

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Minimum Agent Versions

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• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

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Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.66%. Comparing base (c6380c0) to head (2727552).

Additional details and impacted files

@@           Coverage Diff           @@
##            v1.11    #1566   +/-   ##
=======================================
  Coverage   48.66%   48.66%           
=======================================
  Files         226      226           
  Lines       20363    20363           
=======================================
  Hits         9909     9909           
  Misses       9937     9937           
  Partials      517      517           

Flag	Coverage Δ
unittests	48.66% <ø> (ø)

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