doc(installation): add multi-cluster setup section

[dkarpele]

See discussion #1350

Summary by CodeRabbit

• Documentation
  • Added guidance on Image Updater controller placement in multi-cluster environments, clarifying that the controller and ImageUpdater resources must be deployed to the Argo CD management cluster.
  • Added clarification that ImageUpdater resources must be created for the Image Updater to begin modifying workloads.

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[coderabbitai]

Walkthrough

Updates the installation documentation to clarify multi-cluster environment requirements and add a disclaimer about Kubernetes installation. Specifies that the Image Updater controller and ImageUpdater CRs must reside on the Argo CD management cluster and cannot discover CRs from other clusters.

Changes

Cohort / File(s)	Summary
Installation Documentation docs/install/installation.md	Adds "Multi-Cluster Environments" section clarifying controller and CR placement on management cluster; adds disclaimer that Image Updater requires ImageUpdater CRs to modify workloads when deployed as a Kubernetes workload.

Pre-merge checks

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a multi-cluster setup section to the installation documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

docs/install/installation.md (2)

9-18: Clear and accurate multi-cluster constraint documentation.

The new section effectively clarifies the architectural requirement that both the Image Updater controller and ImageUpdater CRs must reside on the management cluster. The use of concrete cluster naming (A/B) and the summary statement are helpful.

Optional enhancement: Consider adding a brief clarification for users who need to manage images across multiple clusters—e.g., whether they would need to run separate Image Updater instances in each cluster. This would help set expectations for more complex topologies.

---

22-23: Minor tone refinement for documentation consistency.

The reassurance is helpful, but the informal tone ("Don't worry") is inconsistent with the rest of the documentation. Consider rephrasing for a more neutral tone while retaining the reassuring message.

Example:

-Don't worry, without creating any ImageUpdater custom resources, it will not start modifying your workloads yet.
+Without creating any ImageUpdater custom resources, the controller will remain inactive and will not modify your workloads.

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📥 Commits

Reviewing files that changed from the base of the PR and between 73263e7 and c78b15c.

📒 Files selected for processing (1)

• docs/install/installation.md (1 hunks)

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• GitHub Check: Analyze (go)
• GitHub Check: Ensure code is correctly linted
• GitHub Check: Ensure registry-scanner Go modules synchronicity and run tests
• GitHub Check: Ensure unit tests are passing
• GitHub Check: build_image

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.80%. Comparing base (73263e7) to head (c78b15c).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1363   +/-   ##
=======================================
  Coverage   70.80%   70.80%           
=======================================
  Files          49       49           
  Lines        4528     4528           
=======================================
  Hits         3206     3206           
  Misses       1125     1125           
  Partials      197      197           

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