fix comment, improve performance

Author: aaronburtle

src/Config/ObjectModel/RuntimeConfig.cs

@@ -353,11 +353,12 @@ public RuntimeConfig(
             // This loader is not used as a part of hot reload and therefore does not need a handler.
             FileSystemRuntimeConfigLoader loader = new(fileSystem, handler: null);
 
+            // Pass the parent's AKV options so @akv() references in child configs can
+            // be resolved using the parent's Key Vault configuration.
+            DeserializationVariableReplacementSettings replacementSettings = new(azureKeyVaultOptions: this.AzureKeyVault, doReplaceEnvVar: true, doReplaceAkvVar: true);
+
             foreach (string dataSourceFile in DataSourceFiles.SourceFiles)
             {
-                // Pass the parent's AKV options so @akv() references in child configs can
-                // be resolved using the parent's Key Vault configuration.
-                DeserializationVariableReplacementSettings replacementSettings = new(azureKeyVaultOptions: this.AzureKeyVault, doReplaceEnvVar: true, doReplaceAkvVar: true);
 
                 if (loader.TryLoadConfig(dataSourceFile, out RuntimeConfig? config, replacementSettings: replacementSettings))
                 {

src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs

@@ -137,7 +137,7 @@ public async Task CanLoadValidMultiSourceConfigWithAutoentities(string configPat
     /// Validates that when a parent config has azure-key-vault options configured,
     /// child configs can resolve @akv('...') references using the parent's AKV configuration.
     /// Uses a local .akv file to simulate Azure Key Vault without requiring a real vault.
-    /// Regression test for https://github.com/Azure/data-api-builder/issues/3271
+    /// Regression test for https://github.com/Azure/data-api-builder/issues/3322
     /// </summary>
     [TestMethod]
     public async Task ChildConfigResolvesAkvReferencesFromParentAkvOptions()