chore(codegen): populate signingName in loader config

Author: trivikr

codegen/smithy-aws-typescript-codegen/src/main/java/software/amazon/smithy/aws/typescript/codegen/AddAwsRuntimeConfig.java

@@ -25,6 +25,7 @@
 import java.util.function.Consumer;
 import java.util.logging.Logger;
 import software.amazon.smithy.aws.traits.ServiceTrait;
+import software.amazon.smithy.aws.traits.auth.SigV4Trait;
 import software.amazon.smithy.aws.typescript.codegen.extensions.AwsRegionExtensionConfiguration;
 import software.amazon.smithy.codegen.core.SymbolProvider;
 import software.amazon.smithy.model.Model;
@@ -169,6 +170,10 @@ public void prepareCustomizations(
             writer.openBlock("const loaderConfig = {", "};", () -> {
                 writer.write("profile: config?.profile,");
                 writer.write("logger: clientSharedValues.logger,");
+                ServiceShape service = settings.getService(model);
+                if (isSigningNameNeededInLoaderConfig(service)) {
+                    writer.write("signingName: $S,", service.expectTrait(SigV4Trait.class).getName());
+                }
             });
         }
     }
@@ -275,4 +280,11 @@ private Map<String, Consumer<TypeScriptWriter>> getEndpointConfigWriters(
                 return Collections.emptyMap();
         }
     }
+
+    private static boolean isSigningNameNeededInLoaderConfig(ServiceShape service) {
+        if (isSigV4Service(service)) {
+            return service.expectTrait(SigV4Trait.class).getName().equals("bedrock");
+        }
+        return false;
+    }
 }