Generate reflection hints for loggers endpoint's responses

Some of the types that are returned are hidden behind a
Map<String, Object> so the operation annotations already been marked
as reflective isn't sufficient.

This commit uses `@RegisterReflectionForBinding` to register the
types that are used as (nested) values in the response maps.

Closes gh-32486

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/logging/LoggersEndpoint.java

@@ -25,10 +25,13 @@ import java.util.NavigableSet;
 import java.util.Set;
 import java.util.TreeSet;
 
+import org.springframework.aot.hint.annotation.RegisterReflectionForBinding;
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
 import org.springframework.boot.actuate.endpoint.annotation.Selector;
 import org.springframework.boot.actuate.endpoint.annotation.WriteOperation;
+import org.springframework.boot.actuate.logging.LoggersEndpoint.GroupLoggerLevels;
+import org.springframework.boot.actuate.logging.LoggersEndpoint.SingleLoggerLevels;
 import org.springframework.boot.logging.LogLevel;
 import org.springframework.boot.logging.LoggerConfiguration;
 import org.springframework.boot.logging.LoggerGroup;
@@ -46,6 +49,7 @@ import org.springframework.util.Assert;
  * @since 2.0.0
  */
 @Endpoint(id = "loggers")
+@RegisterReflectionForBinding({ GroupLoggerLevels.class, SingleLoggerLevels.class })
 public class LoggersEndpoint {
 
 	private final LoggingSystem loggingSystem;

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/logging/LoggersEndpointTests.java

@@ -25,6 +25,10 @@ import java.util.Set;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.annotation.ReflectiveRuntimeHintsRegistrar;
+import org.springframework.aot.hint.predicate.ReflectionHintsPredicates;
+import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
 import org.springframework.boot.actuate.logging.LoggersEndpoint.GroupLoggerLevels;
 import org.springframework.boot.actuate.logging.LoggersEndpoint.LoggerLevels;
 import org.springframework.boot.actuate.logging.LoggersEndpoint.SingleLoggerLevels;
@@ -141,4 +145,19 @@ class LoggersEndpointTests {
 		then(this.loggingSystem).should().setLogLevel("test.member", null);
 	}
 
+	@Test
+	void registersRuntimeHintsForClassesSerializedToJson() {
+		RuntimeHints runtimeHints = new RuntimeHints();
+		new ReflectiveRuntimeHintsRegistrar().registerRuntimeHints(runtimeHints, LoggersEndpoint.class);
+		ReflectionHintsPredicates reflection = RuntimeHintsPredicates.reflection();
+		assertThat(reflection.onType(LoggerLevels.class)).accepts(runtimeHints);
+		assertThat(reflection.onMethod(LoggerLevels.class, "getConfiguredLevel")).accepts(runtimeHints);
+		assertThat(reflection.onType(SingleLoggerLevels.class)).accepts(runtimeHints);
+		assertThat(reflection.onMethod(SingleLoggerLevels.class, "getEffectiveLevel")).accepts(runtimeHints);
+		assertThat(reflection.onMethod(SingleLoggerLevels.class, "getConfiguredLevel")).accepts(runtimeHints);
+		assertThat(reflection.onType(GroupLoggerLevels.class)).accepts(runtimeHints);
+		assertThat(reflection.onMethod(GroupLoggerLevels.class, "getMembers")).accepts(runtimeHints);
+		assertThat(reflection.onMethod(GroupLoggerLevels.class, "getConfiguredLevel")).accepts(runtimeHints);
+	}
+
 }