Fix Advisor retirement recommendation filtering

[cocallaw]

Summary

• normalize Az.Advisor associative extended properties through AdditionalProperties
• preserve existing JSON, dictionary, and cached-property handling
• add regression coverage for mixed retirement and non-retirement recommendations

Validation

• Invoke-Pester ./Tests/AzRetirementMonitor.Tests.ps1 (75 passed)
• PSScriptAnalyzer with PSGallery settings

[Copilot]

Pull request overview

This PR fixes filtering of Azure Advisor retirement recommendations by normalizing how extended properties are read from Az.Advisor recommendation objects, ensuring the ServiceUpgradeAndRetirement subcategory is detected across multiple shapes (JSON string, dictionary, cached object, and Az.Advisor AdditionalProperties dictionaries). It strengthens the module’s robustness while adding regression coverage for mixed retirement/non-retirement datasets.

Changes:

• Update Get-AzAdvisorExtendedProperty to (a) ignore null ExtendedPropertyObject cache entries, (b) fall back between ExtendedProperty and ExtendedProperties, and (c) unwrap Az.Advisor model AdditionalProperties dictionaries.
• Add Pester coverage for null-cache parsing, plural ExtendedProperties, and Az.Advisor associative AdditionalProperties dictionaries to ensure filtering and description building behave correctly.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Tests/AzRetirementMonitor.Tests.ps1	Adds regression tests for ExtendedProperty caching/null behavior and for dictionary/AdditionalProperties shapes used by Az.Advisor.
Private/Get-AzAdvisorExtendedProperty.ps1	Normalizes extraction of extended properties across string/hashtable/materialized and Az.Advisor AdditionalProperties representations.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.