Allow declaring BSON values in entities

turms-server-common/src/main/java/im/turms/server/common/storage/mongo/codec/MongoCodecProvider.java

@@ -21,9 +21,11 @@
 import jakarta.annotation.Nullable;
 
 import lombok.Setter;
+import org.bson.BsonValue;
 import org.bson.codecs.Codec;
 import org.bson.codecs.configuration.CodecProvider;
 import org.bson.codecs.configuration.CodecRegistry;
+import org.bson.conversions.Bson;
 import org.jctools.maps.NonBlockingIdentityHashMap;
 
 /**
@@ -56,7 +58,9 @@ public <T> Codec<T> get(Class<T> clazz, CodecRegistry registry) {
     public <T> MongoCodec<T> getCodec(Class<T> clazz) {
         if (clazz == Object.class) {
             return (MongoCodec<T>) ObjectCodec.INSTANCE;
-        } else if (clazz.getClassLoader() == null) {
+        } else if (clazz.getClassLoader() == null
+                || Bson.class.isAssignableFrom(clazz)
+                || BsonValue.class.isAssignableFrom(clazz)) {
             // Return null if the class is loaded by the bootstrap class loader, which means
             // it is a system class.
             return null;