chore: Update March 2026 section with ALZ Library changes & add feature to support expanding section by default (#4087)

* Update March 2026 section with ALZ Library changes

Added important updates regarding the ALZ Library version and its impact on resource group location mapping in Terraform deployments. Clarified that Bicep AVM-based deployments do not require updates and mentioned the latest SLZ library release.

* docs: update expand shortcode to include title, icon, and expandByDefault attributes

Author: jtracey93

docs/content/whats-new/_index.md

@@ -10,10 +10,16 @@ Here's what's changed in Azure landing zone:
 Azure landing zone IaC accelerator release notes are [HERE]({{% ref "accelerator/accelerator-release-notes" %}})
 {{</hint >}}
 
-{{< expand "March 2026" ">" >}}
+{{< expand title="March 2026" icon=">" expandByDefault="true" >}}
 
 ### March 2026
 
+#### Policy
+
+- **IMPORTANT:** Updated ALZ Library to version: [`2026.01.3`](https://github.com/Azure/Azure-Landing-Zones-Library/releases/tag/platform%2Falz%2F2026.01.3) to handle the mapping of resource group location correctly in the assignment called `Deploy-SvcHealth-BuiltIn` of the built-in definition of [`[Preview]: Configure subscriptions to enable service health alert monitoring rule`](https://www.azadvertizer.net/azpolicyadvertizer/98903777-a9f6-47f5-90a9-acaf62ab01a8.html) which was previously being incorrectly set to `${default_location}` in the ALZ Terraform AVM-based deployment option. Please update your library version to the latest by following the guidance here: [Updating the module and library version](https://azure.github.io/Azure-Landing-Zones/terraform/howtos/update/#updating-the-policy-library)
+  - For clarity the ALZ Bicep AVM-based deployment does not require and update as this was replacing the token placeholder correctly 👍
+  - Sovereign landing zone (SLZ) Terraform deployments should also update to the latest library release of SLZ, which is [`2026.02.2`](https://github.com/Azure/Azure-Landing-Zones-Library/releases/tag/platform%2Fslz%2F2026.02.2)
+
 #### Tooling
 
 - Updated the ***Baseline alerts and monitoring*** integration section in the portal accelerator to deploy the latest release of AMBA (2026-03-06). To read more on the changes, see the [What's new](https://aka.ms/amba/alz/whatsnew) page in the AMBA documentation.

docs/layouts/shortcodes/expand.html

@@ -0,0 +1,14 @@
+{{ $id := substr (sha1 .Inner) 0 8 }}
+{{ $title := or (.Get "title") (.Get 0) "Expand" }}
+{{ $icon := or (.Get "icon") (.Get 1) "↕" }}
+{{ $expandByDefault := eq (.Get "expandByDefault") "true" }}
+<div class="gdoc-expand">
+  <label class="gdoc-expand__head flex justify-between" for="{{ $id }}-{{ .Ordinal }}">
+    <span>{{ $title }}</span>
+    <span>{{ $icon }}</span>
+  </label>
+  <input id="{{ $id }}-{{ .Ordinal }}" type="checkbox" class="gdoc-expand__control hidden"{{ if $expandByDefault }} checked{{ end }} />
+  <div class="gdoc-markdown--nested gdoc-expand__content">
+    {{ .Inner | $.Page.RenderString }}
+  </div>
+</div>