Test v3 actuator API with loggers endpoint

Update `LoggersEndpointWebIntegrationTests` to ensure that the new
v3 media type can be used.

See gh-17929

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

@@ -132,6 +132,15 @@ class LoggersEndpointWebIntegrationTests {
 		verify(this.loggingSystem).setLogLevel("ROOT", LogLevel.DEBUG);
 	}
 
+	@WebEndpointTest
+	void setLoggerUsingActuatorV3JsonShouldSetLogLevel() {
+		this.client.post().uri("/actuator/loggers/ROOT")
+				.contentType(MediaType.parseMediaType(ActuatorMediaType.V3_JSON))
+				.bodyValue(Collections.singletonMap("configuredLevel", "debug")).exchange().expectStatus()
+				.isNoContent();
+		verify(this.loggingSystem).setLogLevel("ROOT", LogLevel.DEBUG);
+	}
+
 	@WebEndpointTest
 	void setLoggerGroupUsingActuatorV2JsonShouldSetLogLevel() {
 		this.client.post().uri("/actuator/loggers/test")
@@ -162,7 +171,7 @@ class LoggersEndpointWebIntegrationTests {
 	@WebEndpointTest
 	void setLoggerWithNullLogLevel() {
 		this.client.post().uri("/actuator/loggers/ROOT")
-				.contentType(MediaType.parseMediaType(ActuatorMediaType.V2_JSON))
+				.contentType(MediaType.parseMediaType(ActuatorMediaType.V3_JSON))
 				.bodyValue(Collections.singletonMap("configuredLevel", null)).exchange().expectStatus().isNoContent();
 		verify(this.loggingSystem).setLogLevel("ROOT", null);
 	}
@@ -170,7 +179,7 @@ class LoggersEndpointWebIntegrationTests {
 	@WebEndpointTest
 	void setLoggerWithNoLogLevel() {
 		this.client.post().uri("/actuator/loggers/ROOT")
-				.contentType(MediaType.parseMediaType(ActuatorMediaType.V2_JSON)).bodyValue(Collections.emptyMap())
+				.contentType(MediaType.parseMediaType(ActuatorMediaType.V3_JSON)).bodyValue(Collections.emptyMap())
 				.exchange().expectStatus().isNoContent();
 		verify(this.loggingSystem).setLogLevel("ROOT", null);
 	}
@@ -178,7 +187,7 @@ class LoggersEndpointWebIntegrationTests {
 	@WebEndpointTest
 	void setLoggerGroupWithNullLogLevel() {
 		this.client.post().uri("/actuator/loggers/test")
-				.contentType(MediaType.parseMediaType(ActuatorMediaType.V2_JSON))
+				.contentType(MediaType.parseMediaType(ActuatorMediaType.V3_JSON))
 				.bodyValue(Collections.singletonMap("configuredLevel", null)).exchange().expectStatus().isNoContent();
 		verify(this.loggingSystem).setLogLevel("test.member1", null);
 		verify(this.loggingSystem).setLogLevel("test.member2", null);
@@ -187,7 +196,7 @@ class LoggersEndpointWebIntegrationTests {
 	@WebEndpointTest
 	void setLoggerGroupWithNoLogLevel() {
 		this.client.post().uri("/actuator/loggers/test")
-				.contentType(MediaType.parseMediaType(ActuatorMediaType.V2_JSON)).bodyValue(Collections.emptyMap())
+				.contentType(MediaType.parseMediaType(ActuatorMediaType.V3_JSON)).bodyValue(Collections.emptyMap())
 				.exchange().expectStatus().isNoContent();
 		verify(this.loggingSystem).setLogLevel("test.member1", null);
 		verify(this.loggingSystem).setLogLevel("test.member2", null);