dev: add new backend settings needed for session tracking

dev/constellations-backend.tf

@@ -66,7 +66,9 @@ resource "azurerm_linux_web_app" "cx_backend" {
 
   app_settings = {
     "AZURE_COSMOS_CONNECTIONSTRING" = azurerm_cosmosdb_account.cx_backend.connection_strings[0]
+    "CX_CORS_ORIGINS"               = "https://${var.tld}"
     "CX_PREVIEW_BASE_URL"           = "https://${azurerm_cdn_endpoint_custom_domain.cxdata.host_name}/previews"
+    "CX_SESSION_SECRETS"            = var.sessionSecrets
     "CX_SUPERUSER_ACCOUNT_ID"       = var.superuserAccountId
     "KEYCLOAK_URL"                  = "https://${var.tld}/auth/"
   }

dev/variables.tf

@@ -25,6 +25,11 @@ variable "cxkeycloakAdminPassword" {
   sensitive   = true
 }
 
+variable "sessionSecrets" {
+  description = "Space-separated list of secrets for backend session management"
+  sensitive   = true
+}
+
 variable "tmpVaultId" {
   description = "The Azure resource ID of the keyvault to use"
 }