Add serialization configuration for cache.support.NullValue

This commit makes sure to register serialization of null values for usage within a native image.

Closes: #2403

Author: christophstrobl

src/main/java/org/springframework/data/redis/aot/RedisRuntimeHints.java

@@ -31,6 +31,7 @@
 import org.springframework.data.keyvalue.repository.config.QueryCreatorType;
 import org.springframework.data.keyvalue.repository.query.KeyValuePartTreeQuery;
 import org.springframework.data.keyvalue.repository.support.KeyValueRepositoryFactoryBean;
+import org.springframework.data.redis.cache.RedisCacheManager;
 import org.springframework.data.redis.connection.*;
 import org.springframework.data.redis.core.*;
 import org.springframework.data.redis.core.convert.KeyspaceConfiguration;
@@ -59,6 +60,10 @@ class RedisRuntimeHints implements RuntimeHintsRegistrar {
 	@Override
 	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 
+		// CACHE
+		hints.serialization().registerType(org.springframework.cache.support.NullValue.class,
+				hint -> hint.onReachableType(TypeReference.of(RedisCacheManager.class)));
+
 		// REFLECTION
 		hints.reflection().registerTypes(Arrays.asList(TypeReference.of(RedisConnection.class),
 				TypeReference.of(StringRedisConnection.class), TypeReference.of(DefaultedRedisConnection.class),