Upgrade to Jackson 2.21.2

The Jackson team have ended support for Jackson 2.19.x (and 2.20.x).
In response to this, this commit upgrades to Jackson 2.21.2. 2.21.x
is designated as an LTS release so future minor upgrades should not
be necessary.

Closes gh-49365

Author: wilkinsona

gradle.properties

@@ -11,7 +11,7 @@ checkstyleToolVersion=10.12.4
 commonsCodecVersion=1.18.0
 graalVersion=22.3
 hamcrestVersion=3.0
-jacksonVersion=2.19.4
+jacksonVersion=2.21.2
 javaFormatVersion=0.0.47
 junitJupiterVersion=5.12.2
 kotlinVersion=1.9.25

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/context/properties/ConfigurationPropertiesReportEndpoint.java

@@ -180,13 +180,19 @@ protected void configureJsonMapper(JsonMapper.Builder builder) {
 		builder.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
 		builder.configure(SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS, false);
 		builder.configure(MapperFeature.USE_STD_BEAN_NAMING, true);
-		builder.serializationInclusion(Include.NON_NULL);
+		configureInclusion(builder);
 		applyConfigurationPropertiesFilter(builder);
 		applySerializationModifier(builder);
 		builder.addModule(new JavaTimeModule());
 		builder.addModule(new ConfigurationPropertiesModule());
 	}
 
+	@SuppressWarnings("deprecation")
+	private void configureInclusion(JsonMapper.Builder builder) {
+		// Avoid using defaultPropertyInclusion to retain compatibility with Jackson 2.19.
+		builder.serializationInclusion(Include.NON_NULL);
+	}
+
 	private void applyConfigurationPropertiesFilter(JsonMapper.Builder builder) {
 		builder.annotationIntrospector(new ConfigurationPropertiesAnnotationIntrospector());
 		builder