Messagepack (#12)

* add messagepack attributes

* fix isnullorempty

* bump api version

---------

Co-authored-by: rootdarkarchon <root.darkarchon@outlook.com>

MareSynchronosAPI/Dto/Group/GroupPairDto.cs

@@ -1,7 +1,9 @@
 using MareSynchronos.API.Data;
+using MessagePack;
 
 namespace MareSynchronos.API.Dto.Group;
 
+[MessagePackObject(keyAsPropertyName: true)]
 public record GroupPairDto(GroupData Group, UserData User) : GroupDto(Group)
 {
     public string UID => User.UID;