Order kotlinxJsonCodecCustomizer so user-provided customizer can go after it

Closes gh-50428

Signed-off-by: Dmitry Sulman <dmitry.sulman@gmail.com>

module/spring-boot-http-codec/src/main/java/org/springframework/boot/http/codec/autoconfigure/CodecsAutoConfiguration.java

@@ -103,6 +103,7 @@ public final class CodecsAutoConfiguration {
 	static class KotlinxSerializationJsonCodecConfiguration {
 
 		@Bean
+		@Order(0)
 		@ConditionalOnBean(Json.class)
 		CodecCustomizer kotlinxJsonCodecCustomizer(Json json, ResourceLoader resourceLoader) {
 			ClassLoader classLoader = resourceLoader.getClassLoader();

module/spring-boot-http-codec/src/test/java/org/springframework/boot/http/codec/autoconfigure/CodecsAutoConfigurationTests.java

@@ -160,6 +160,16 @@ class CodecsAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void userProvidedCustomizerCanOverrideKotlinxJsonCodecCustomizer() {
+		this.contextRunner.withUserConfiguration(KotlinxJsonConfiguration.class, CodecCustomizerConfiguration.class)
+			.run((context) -> {
+				List<CodecCustomizer> codecCustomizers = context.getBean(CodecCustomizers.class).codecCustomizers;
+				assertThat(codecCustomizers).hasSize(3);
+				assertThat(codecCustomizers.get(2)).isInstanceOf(TestCodecCustomizer.class);
+			});
+	}
+
 	@SuppressWarnings("unchecked")
 	private <T> T findEncoder(AssertableApplicationContext context, Class<T> encoderClass) {
 		ServerCodecConfigurer configurer = ServerCodecConfigurer.create();