Add system-assigned managed identities to web site module configuration

Author: Pavan-Microsoft

infra/main_custom.bicep

@@ -1567,6 +1567,9 @@ module webSite 'modules/web-sites.bicep' = {
     location: location
     kind: 'app,linux'
     serverFarmResourceId: webServerFarm.?outputs.resourceId
+    managedIdentities: {
+      systemAssigned: true
+    }
     siteConfig: {
       //linuxFxVersion: 'DOCKER|${frontendContainerRegistryHostname}/${frontendContainerImageName}:${frontendContainerImageTag}'
       minTlsVersion: '1.2'