Register a binder for parts that returns unsatisfied

http/src/main/java/io/micronaut/http/bind/DefaultRequestBinderRegistry.java

@@ -262,6 +262,9 @@ protected void registerDefaultAnnotationBinders(Map<Class<? extends Annotation>,
         RequestBeanAnnotationBinder<Object> requestBeanAnnotationBinder = new RequestBeanAnnotationBinder<>(this, conversionService);
         byAnnotation.put(requestBeanAnnotationBinder.getAnnotationType(), requestBeanAnnotationBinder);
 
+        PartAnnotationBinder<Object> partAnnotationBinder = new PartAnnotationBinder<>(conversionService);
+        byAnnotation.put(partAnnotationBinder.getAnnotationType(), partAnnotationBinder);
+
         if (KOTLIN_COROUTINES_SUPPORTED) {
             ContinuationArgumentBinder continuationArgumentBinder = new ContinuationArgumentBinder();
             byType.put(continuationArgumentBinder.argumentType().typeHashCode(), continuationArgumentBinder);

http/src/main/java/io/micronaut/http/bind/binders/PartAnnotationBinder.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2017-2022 original authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micronaut.http.bind.binders;
+
+import io.micronaut.core.bind.annotation.AbstractAnnotatedArgumentBinder;
+import io.micronaut.core.convert.ArgumentConversionContext;
+import io.micronaut.core.convert.ConversionService;
+import io.micronaut.http.HttpRequest;
+import io.micronaut.http.annotation.Part;
+
+/**
+ * Skips binding parts because they should be handled by a multipart processor.
+ *
+ * @param <T> The part type
+ * @author James Kleeh
+ * @since 3.6.4
+ */
+public class PartAnnotationBinder<T> extends AbstractAnnotatedArgumentBinder<Part, T, HttpRequest<?>> implements AnnotatedRequestArgumentBinder<Part, T> {
+
+    public PartAnnotationBinder(ConversionService<?> conversionService) {
+        super(conversionService);
+    }
+
+    @Override
+    public BindingResult<T> bind(ArgumentConversionContext<T> context, HttpRequest<?> source) {
+        //noinspection unchecked
+        return BindingResult.UNSATISFIED;
+    }
+
+    @Override
+    public Class<Part> getAnnotationType() {
+        return Part.class;
+    }
+}