docs: administration: transport-security: document certificate reload

[eschabell]

Document that Fluent Bit reloads TLS certificates from disk when it creates a new session, covering the files it watches, how it detects changes including inode swaps from Kubernetes secret updates, that established sessions keep their existing context, and what happens when a reload fails.

Note, updates for code changes without corresponding docs PR.

Summary by CodeRabbit

• Documentation
  • Added guidance for automatic TLS certificate and CA file reloading in Fluent Bit 5.1 and later.
  • Documented support for both input and output plugins.
  • Clarified that existing sessions remain unchanged while new sessions use updated certificates.
  • Explained error handling and retry behavior when certificate reloading fails.

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

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Run ID: e317905a-92a4-4221-857a-6e1be7f25691

📥 Commits

Reviewing files that changed from the base of the PR and between 2023ce8 and bb4f16c.

📒 Files selected for processing (1)

• administration/transport-security.md

📝 Walkthrough

Walkthrough

Changes

TLS certificate reload

Layer / File(s)	Summary
Document automatic TLS reload behavior administration/transport-security.md	Documents certificate and CA file change detection, TLS context rebuilding for new sessions, retention of existing session contexts, and retry behavior after reload failures.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: patrick-stephens

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely identifies the documentation change for TLS certificate reload behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@administration/transport-security.md`:
- Line 220: Update the TLS session reload description to distinguish tls.ca_path
as a directory that Fluent Bit scans from tls.ca_file, tls.crt_file, and
tls.key_file as individual files. Describe reload detection accurately without
implying that tls.ca_path itself is a file reference.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f3669a69-33e2-4e49-997f-86f5ebe3b2a6

📥 Commits

Reviewing files that changed from the base of the PR and between 0eb06a6 and 2023ce8.

📒 Files selected for processing (1)

• administration/transport-security.md

[eschabell]

@patrick-stephens ready for review!