upgrade smithy, correct serialization of empty-prefix httpPrefixHeaders (#582)

Author: lucix-aws

codegen/gradle.properties

@@ -1,2 +1,2 @@
-smithyVersion=1.52.1
+smithyVersion=1.58.0
 smithyGradleVersion=0.7.0

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/integration/HttpBindingProtocolGenerator.java

@@ -862,6 +862,10 @@ private void writeHttpBindingMember(
                             writeHeaderBinding(context, memberShape, operand, location, "locationName", "encoder");
                             break;
                         case PREFIX_HEADERS:
+                            // the prefix is allowed to be empty for headers, this simply means that there is none
+                            // and map keys are used directly as headers
+                            var prefix = binding.getLocationName();
+
                             MemberShape valueMemberShape = model.expectShape(targetShape.getId(),
                                     MapShape.class).getValue();
                             Shape valueMemberTarget = model.expectShape(valueMemberShape.getTarget());
@@ -872,7 +876,7 @@ private void writeHttpBindingMember(
                                         + valueMemberShape.getId());
                             }
 
-                            writer.write("hv := encoder.Headers($S)", getCanonicalHeader(locationName));
+                            writer.write("hv := encoder.Headers($S)", getCanonicalHeader(prefix));
                             writer.addUseImports(SmithyGoDependency.NET_HTTP);
                             writer.openBlock("for mapKey, mapVal := range $L {", "}", operand, () -> {
                                 writeHeaderBinding(context, valueMemberShape, "mapVal", location,