Add httpErrorCode trait support

Author: JordonPhillips

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/integrations/BuiltinsIntegration.java

@@ -15,6 +15,7 @@
 import software.amazon.smithy.docgen.core.interceptors.DeprecatedInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.ErrorFaultInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.ExternalDocsInterceptor;
+import software.amazon.smithy.docgen.core.interceptors.HttpErrorInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.HttpHeaderInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.HttpInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.HttpLabelInterceptor;
@@ -93,6 +94,7 @@ public List<? extends CodeInterceptor<? extends CodeSection, DocWriter>> interce
                 new XmlAttributeInterceptor(),
                 new XmlNameInterceptor(),
                 new XmlFlattenedInterceptor(),
+                new HttpErrorInterceptor(),
                 new HttpHeaderInterceptor(),
                 new HttpPrefixHeadersInterceptor(),
                 new HttpQueryParamsInterceptor(),

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/interceptors/HttpErrorInterceptor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.docgen.core.interceptors;
+
+import software.amazon.smithy.docgen.core.sections.ProtocolSection;
+import software.amazon.smithy.docgen.core.writers.DocWriter;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.HttpErrorTrait;
+
+/**
+ * Adds the http response code for errors from the
+ * <a href="https://smithy.io/2.0/spec/http-bindings.html#httperror-trait">
+ * httpError trait</a> if the protocol supports it.
+ */
+public final class HttpErrorInterceptor extends ProtocolTraitInterceptor<HttpErrorTrait> {
+    @Override
+    protected Class<HttpErrorTrait> getTraitClass() {
+        return HttpErrorTrait.class;
+    }
+
+    @Override
+    protected ShapeId getTraitId() {
+        return HttpErrorTrait.ID;
+    }
+
+    @Override
+    void write(DocWriter writer, String previousText, ProtocolSection section, HttpErrorTrait trait) {
+        writer.putContext("code", trait.getCode());
+        writer.write("""
+                $B ${code:`}
+
+                $L""", "HTTP Error Code:", previousText);
+    }
+}