Handle Gson explicitly in CodecsAutoConfigurationTests

The change in gh-50447 added gson on the runtime classpath, which broke
a test that looks for "any" JSON support, but only filtered Jackson and
Jackson 2.

This commit adds an explicit optional dependency to gson and adapt the
test accordingly.

See gh-50447

Author: snicoll

module/spring-boot-http-codec/build.gradle

@@ -30,6 +30,7 @@ dependencies {
 
 	optional(project(":core:spring-boot-autoconfigure"))
 	optional(project(":core:spring-boot-test"))
+	optional(project(":module:spring-boot-gson"))
 	optional(project(":module:spring-boot-jackson"))
 	optional(project(":module:spring-boot-jackson2"))
 	optional(project(":module:spring-boot-kotlinx-serialization-json"))

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

@@ -20,6 +20,7 @@
 import java.util.Map;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
 import kotlinx.serialization.json.Json;
 import org.junit.jupiter.api.Test;
 import tools.jackson.databind.json.JsonMapper;
@@ -150,7 +151,7 @@ void kotlinSerializationUsesLimitedPredicateWhenOtherJsonConverterIsAvailable()
 	@Test
 	void kotlinSerializationUsesUnrestrictedPredicateWhenNoOtherJsonConverterIsAvailable() {
 		FilteredClassLoader classLoader = new FilteredClassLoader(JsonMapper.class.getPackage().getName(),
-				ObjectMapper.class.getPackage().getName());
+				ObjectMapper.class.getPackage().getName(), Gson.class.getPackage().getName());
 		this.contextRunner.withClassLoader(classLoader)
 			.withUserConfiguration(KotlinxJsonConfiguration.class)
 			.run((context) -> {