Add basic write support via automapper

osu.Game/Database/RealmObjectExtensions.cs

@@ -19,7 +19,33 @@ namespace osu.Game.Database
 {
     public static class RealmObjectExtensions
     {
-        private static readonly IMapper mapper = new MapperConfiguration(c =>
+        private static readonly IMapper write_mapper = new MapperConfiguration(c =>
+        {
+            c.ShouldMapField = fi => false;
+            // If we want to limit this further, we can avoid mapping properties with no setter that are not IList<>.
+            // Takes a bit of effort to determine whether this is the case though, see https://stackoverflow.com/questions/951536/how-do-i-tell-whether-a-type-implements-ilist
+            c.ShouldMapProperty = pi => pi.SetMethod?.IsPublic == true;
+
+            c.CreateMap<RealmKeyBinding, RealmKeyBinding>();
+            c.CreateMap<BeatmapMetadata, BeatmapMetadata>();
+            c.CreateMap<BeatmapDifficulty, BeatmapDifficulty>();
+            c.CreateMap<RulesetInfo, RulesetInfo>();
+            c.CreateMap<ScoreInfo, ScoreInfo>();
+            c.CreateMap<RealmUser, RealmUser>();
+            c.CreateMap<RealmFile, RealmFile>();
+            c.CreateMap<RealmNamedFileUsage, RealmNamedFileUsage>();
+            c.CreateMap<BeatmapInfo, BeatmapInfo>();
+            c.CreateMap<BeatmapSetInfo, BeatmapSetInfo>();
+            c.AddGlobalIgnore(nameof(RealmObjectBase.ObjectSchema));
+
+            c.ForAllMaps((a, b) =>
+            {
+                b.PreserveReferences();
+                b.MaxDepth(2);
+            });
+        }).CreateMapper();
+
+        private static readonly IMapper read_mapper = new MapperConfiguration(c =>
         {
             c.ShouldMapField = fi => false;
             // If we want to limit this further, we can avoid mapping properties with no setter that are not IList<>.
@@ -36,6 +62,7 @@ namespace osu.Game.Database
             c.CreateMap<RealmNamedFileUsage, RealmNamedFileUsage>();
             c.CreateMap<BeatmapInfo, BeatmapInfo>();
             c.CreateMap<BeatmapSetInfo, BeatmapSetInfo>();
+            c.AddGlobalIgnore(nameof(RealmObjectBase.ObjectSchema));
 
             c.ForAllMaps((a, b) =>
             {
@@ -77,7 +104,12 @@ namespace osu.Game.Database
             if (!item.IsManaged)
                 return item;
 
-            return mapper.Map<T>(item);
+            return read_mapper.Map<T>(item);
+        }
+
+        public static void CopyChangesToRealm<T>(this T source, T destination) where T : RealmObjectBase
+        {
+            write_mapper.Map(source, destination);
         }
 
         public static List<ILive<T>> ToLiveUnmanaged<T>(this IEnumerable<T> realmList)