Use IConfigurationSection in EnableTokenAcquistion Internal and fix 1…

…583 (#1582)

* use IConfigSection

* fix warning

src/Microsoft.Identity.Web/WebApiExtensions/WebApiBuilders.cs

@@ -23,28 +23,29 @@ public static class WebApiBuilders
         /// <param name="configureConfidentialClientApplicationOptions">The action to configure <see cref="ConfidentialClientApplicationOptions"/>.</param>
         /// <param name="authenticationScheme">Authentication scheme.</param>
         /// <param name="services">The services being configured.</param>
-        /// <param name="configuration">Configuration.</param>
+        /// <param name="configuration">IConfigurationSection.</param>
         /// <returns>The authentication builder to chain.</returns>
         public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder EnableTokenAcquisition(
             Action<ConfidentialClientApplicationOptions> configureConfidentialClientApplicationOptions,
             string authenticationScheme,
             IServiceCollection services,
-            IConfiguration? configuration)
+            IConfigurationSection? configuration)
         {
             services.AddOptions<ConfidentialClientApplicationOptions>(authenticationScheme)
                             .Configure<IOptionsMonitor<MergedOptions>>((
                                ccaOptions, mergedOptionsMonitor) =>
                             {
                                 configureConfidentialClientApplicationOptions(ccaOptions);
                                 MergedOptions mergedOptions = mergedOptionsMonitor.Get(authenticationScheme);
+                                configuration.Bind(mergedOptions);
                                 MergedOptions.UpdateMergedOptionsFromConfidentialClientApplicationOptions(ccaOptions, mergedOptions);
                             });
 
             services.AddTokenAcquisition();
 
             return new MicrosoftIdentityAppCallsWebApiAuthenticationBuilder(
                 services,
-                configuration as IConfigurationSection);
+                configuration);
         }
     }
 }