Fix identity name and cost esitmation for aca

Author: 1yefuwang1

README.md

@@ -66,6 +66,7 @@ Pricing varies per region and usage, so it isn't possible to predict exact costs
 However, you can try the [Azure pricing calculator](https://azure.com/e/a87a169b256e43c089015fda8182ca87) for the resources below.
 
 - Azure App Service: Basic Tier with 1 CPU core, 1.75 GB RAM. Pricing per hour. [Pricing](https://azure.microsoft.com/pricing/details/app-service/linux/)
+- Azure Container Apps: Consumption plan with 1 CPU core, 2.0 GB RAM. Pricing with Pay-as-You-Go. [Pricing](https://azure.microsoft.com/pricing/details/container-apps/)
 - Azure OpenAI: Standard tier, GPT and Ada models. Pricing per 1K tokens used, and at least 1K tokens are used per question. [Pricing](https://azure.microsoft.com/pricing/details/cognitive-services/openai-service/)
 - Azure AI Document Intelligence: SO (Standard) tier using pre-built layout. Pricing per document page, sample documents have 261 pages total. [Pricing](https://azure.microsoft.com/pricing/details/form-recognizer/)
 - Azure AI Search: Basic tier, 1 replica, free level of semantic search. Pricing per hour. [Pricing](https://azure.microsoft.com/pricing/details/search/)

infra/main.bicep

@@ -394,16 +394,16 @@ module acaBackend 'core/host/container-app-upsert.bicep' = if (deploymentTarget
   params: {
     name: !empty(backendServiceName) ? backendServiceName : '${abbrs.webSitesContainerApps}backend-${resourceToken}'
     location: location
-    identityName: (deploymentTarget == 'containerapps') ? acaIdentity.name : ''
+    identityName: (deploymentTarget == 'containerapps') ? acaIdentityName : ''
     exists: webAppExists
     workloadProfile: azureContainerAppsWorkloadProfile
     containerRegistryName: (deploymentTarget == 'containerapps') ? containerApps.outputs.registryName : ''
     containerAppsEnvironmentName: (deploymentTarget == 'containerapps') ? containerApps.outputs.environmentName : ''
     identityType: 'UserAssigned'
     tags: union(tags, { 'azd-service-name': 'backend' })
     targetPort: 8000
-    containerCpuCoreCount: '2.0'
-    containerMemory: '4Gi'
+    containerCpuCoreCount: '1.0'
+    containerMemory: '2Gi'
     allowedOrigins: [ allowedOrigin ]
     env: {
       AZURE_STORAGE_ACCOUNT: storage.outputs.name