Add asyncCredentialUpdateEnabled getter in builder

Author: S-Saranya1

services/sts/src/main/java/software/amazon/awssdk/services/sts/auth/StsCredentialsProvider.java

@@ -131,14 +131,6 @@ public Duration prefetchTime() {
         return prefetchTime;
     }
 
-    /**
-     * Whether the provider should fetch credentials asynchronously in the background.
-     * <p>By default, this is false.</p>
-     */
-    public Boolean asyncCredentialUpdateEnabled() {
-        return asyncCredentialUpdateEnabled;
-    }
-
     @Override
     public String toString() {
         return ToString.create(providerName());
@@ -238,5 +230,13 @@ public B prefetchTime(Duration prefetchTime) {
         public T build() {
             return providerConstructor.apply((B) this);
         }
+
+        /**
+         * Whether the provider should fetch credentials asynchronously in the background.
+         * <p>By default, this is false.</p>
+         */
+        Boolean asyncCredentialUpdateEnabled() {
+            return asyncCredentialUpdateEnabled;
+        }
     }
 }

services/sts/src/main/java/software/amazon/awssdk/services/sts/auth/StsWebIdentityTokenFileCredentialsProvider.java

@@ -107,14 +107,18 @@ private StsWebIdentityTokenFileCredentialsProvider(Builder builder) {
                                                         .webIdentityTokenFile(credentialProperties.webIdentityTokenFile())
                                                         .build();
 
-            credentialsProviderLocal =
+            StsAssumeRoleWithWebIdentityCredentialsProvider.Builder providerBuilder =
                 StsAssumeRoleWithWebIdentityCredentialsProvider.builder()
                                                                .stsClient(builder.stsClient)
                                                                .refreshRequest(supplier)
                                                                .staleTime(this.staleTime())
-                                                               .prefetchTime(this.prefetchTime())
-                                                               .asyncCredentialUpdateEnabled(this.asyncCredentialUpdateEnabled())
-                                                               .build();
+                                                               .prefetchTime(this.prefetchTime());
+            
+            if (builder.asyncCredentialUpdateEnabled() != null) {
+                providerBuilder.asyncCredentialUpdateEnabled(builder.asyncCredentialUpdateEnabled());
+            }
+            
+            credentialsProviderLocal = providerBuilder.build();
         } catch (RuntimeException e) {
             // If we couldn't load the credentials provider for some reason, save an exception describing why. This exception
             // will only be raised on calls to getCredentials. We don't want to raise an exception here because it may be