[AKS] Add --enable-hosted-system, --system-node-subnet-id and --node-subnet-id to az aks update

[reneeli123]

🤖 PR Validation — ⚠️ Review suggested

Breaking Changes
⚠️ None

⚠️Azure CLI Extensions Breaking Change Test

⚠️aks-preview

rule	cmd_name	rule_message	suggest_message
⚠️ 1006 - ParaAdd	aks update	cmd aks update added parameter enable_hosted_system
⚠️ 1006 - ParaAdd	aks update	cmd aks update added parameter node_subnet_id
⚠️ 1006 - ParaAdd	aks update	cmd aks update added parameter system_node_subnet_id

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Related command

az aks update -n $auto-cluster -g $auto-rg --enable-hosted-system --apiserver-subnet-id(optional for byo) --node-subnet-id(optional for byo) --system-node-subnet-id(optional for byo)

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[azure-client-tools-bot-prd]

Hi reneeli123,
Please write the description of changes which can be perceived by customers into HISTORY.rst.
If you want to release a new extension version, please update the version in pyproject.toml (or setup.py, if the extension has not migrated yet) as well.

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[Copilot]

Pull request overview

This PR extends the aks-preview extension’s az aks update flow to support converting an existing Automatic SKU cluster to use a Managed System Pool (hosted system), optionally alongside BYO VNet subnet configuration.

Changes:

• Adds --enable-hosted-system, --system-node-subnet-id, and --node-subnet-id to az aks update (params, custom entrypoint wiring, and help).
• Implements update-time handling for hosted_system_profile via update_hosted_system_profile, including validation and SKU-specific error messaging.
• Adds unit test coverage for hosted-system update behavior and documents the change in HISTORY.rst.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/aks-preview/HISTORY.rst	Documents the new az aks update parameters and scenario in the next release entry.
src/aks-preview/azext_aks_preview/tests/latest/test_managed_cluster_decorator.py	Adds unit tests for hosted-system update behavior (enablement, BYO trio, and validation failures).
src/aks-preview/azext_aks_preview/managed_cluster_decorator.py	Adds hosted-system update implementation + refines validation/error messaging for update mode; wires into update flow.
src/aks-preview/azext_aks_preview/custom.py	Wires new parameters into the aks_update command signature so they reach the decorator.
src/aks-preview/azext_aks_preview/_params.py	Exposes the new CLI arguments (including validators) under aks update.
src/aks-preview/azext_aks_preview/_help.py	Adds help text and examples for the new update flags and BYO subnet trio behavior.

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[Aditya Pujara (a0x1ab)]

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[Aditya Pujara (a0x1ab)]

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