Add serialization hint for ProblemDetail

Prior to this commit, a Spring web application would not be able to
serialize a `ProblemDetail` object instance in a Native Image, as
serialization hints would be missing.

This commit adds a RuntimeHints registrar that processes the
`ProblemDetail` type accordingly during the AOT phase.

Fixes gh-29801

spring-web/src/test/java/org/springframework/http/converter/json/ProblemDetailRuntimeHintsTests.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2002-2023 the original author or 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 org.springframework.http.converter.json;
+
+
+import java.util.List;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
+import org.springframework.beans.factory.aot.AotServices;
+import org.springframework.http.ProblemDetail;
+import org.springframework.util.ClassUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ProblemDetailRuntimeHints}.
+ * @author Brian Clozel
+ */
+class ProblemDetailRuntimeHintsTests {
+
+	private final RuntimeHints hints = new RuntimeHints();
+
+	@BeforeEach
+	void setup() {
+		AotServices.factories().load(RuntimeHintsRegistrar.class)
+				.forEach(registrar -> registrar.registerHints(this.hints,
+						ClassUtils.getDefaultClassLoader()));
+	}
+
+	@Test
+	void getterMethodsShouldHaveReflectionHints() {
+		List<String> methodNames = List.of("getType", "getTitle", "getStatus", "getDetail", "getInstance", "getProperties");
+		for (String methodName : methodNames) {
+			assertThat(RuntimeHintsPredicates.reflection().onMethod(ProblemDetail.class, methodName)).accepts(this.hints);
+		}
+	}
+
+}