fix(bicep): guard EventHub and Fabric vars against ARM eager-evaluation; fix README headings

Author: Yamini-Microsoft

README.md

@@ -41,7 +41,7 @@ If you'd like to customize the solution accelerator, here are some common areas
 
 <br/>
 
-### Additional resources
+## Resources
 
 [What's New in Microsoft Fabric](https://learn.microsoft.com/en-us/fabric/fundamentals/whats-new)
 
@@ -53,7 +53,8 @@ If you'd like to customize the solution accelerator, here are some common areas
 
 <br/>
 
-### Key features
+## Features
+
 <details>
   <summary>Click to learn more about the key features this solution enables</summary> 
 
@@ -79,6 +80,8 @@ If you'd like to customize the solution accelerator, here are some common areas
 Quick deploy
 </h2>
 
+## Getting Started
+
 ### How to install or deploy
 
 Follow these steps to deploy the solution to your own Azure subscription:
@@ -190,6 +193,8 @@ Use cases can be summarized as below:
 Supporting documentation
 </h2>
 
+## Guidance
+
 ### Security guidelines
 
 This template uses Azure Key Vault to store all connections to communicate between resources.

infra/main.bicep

@@ -65,23 +65,20 @@ param existingFabricCapacityName string = ''
 
 // ============================================================================
 // Determine whether to use existing resources
-// Scenarios:
-// 1. Create new namespace + new event hub: existingEventHubNamespaceId not set
-// 2. Use existing namespace, create new event hub: existingEventHubNamespaceId is set
-//
-// NOTE: A new Event Hub is always created to avoid mixing unrelated event types.
-// This follows best practices for Event Hub usage.
 // ============================================================================
 
-var useExistingEventHubNamespace = !empty(existingEventHubNamespaceId)
-// Extract namespace name from resource ID if using existing, otherwise generate new name
-var eventHubNamespaceNameFromId = useExistingEventHubNamespace ? last(split(existingEventHubNamespaceId, '/')) : ''
-// Parse subscription ID and resource group from the namespace resource ID
-// This enables cross-subscription and cross-resource-group deployments
-// Example: namespace in sub-123/rg-shared while deploying to sub-456/rg-demo
-var eventHubNamespaceSubscriptionId = useExistingEventHubNamespace ? split(existingEventHubNamespaceId, '/')[2] : ''
-var eventHubNamespaceResourceGroup = useExistingEventHubNamespace ? split(existingEventHubNamespaceId, '/')[4] : ''
-var useExistingFabricCapacity = !empty(existingFabricCapacityName)
+// Use an existing namespace if a valid resource ID is provided; otherwise create a new one.
+// A new Event Hub is always created to avoid mixing unrelated event types.
+var useExistingEventHubNamespace = startsWith(existingEventHubNamespaceId, '/subscriptions/')
+// Fallback placeholder ensures split() is always called on a well-formed resource ID.
+var _safeEventHubNamespaceId = useExistingEventHubNamespace
+  ? existingEventHubNamespaceId
+  : '/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/placeholder/providers/Microsoft.EventHub/namespaces/placeholder'
+var eventHubNamespaceNameFromId = last(split(_safeEventHubNamespaceId, '/'))
+var eventHubNamespaceSubscriptionId = split(_safeEventHubNamespaceId, '/')[2]
+var eventHubNamespaceResourceGroup = split(_safeEventHubNamespaceId, '/')[4]
+// Use an existing Fabric capacity if a valid name is provided; otherwise create a new one.
+var useExistingFabricCapacity = !empty(existingFabricCapacityName) && !startsWith(existingFabricCapacityName, '$')
 
 var solutionSuffix = toLower(trim(replace(
   replace(