Add player settings feature and settings API

src/RecNet.Domain/Profiles/Profile.cs

@@ -36,6 +36,7 @@ public class Profile
     public DateTimeOffset CreatedAt { get; private set; }
 
     public Avatar Avatar { get; private set; } = Avatar.Empty;
+    public ICollection<PlayerSetting> Settings { get; } = [];
 
     public static Profile Create(
         string name, 
@@ -86,6 +87,19 @@ public class Profile
     public void SetAvatar(Avatar avatar)
         => Avatar = avatar ?? throw new DomainException("Avatar is required.");
     
+    public void SetSetting(string key, string value)
+    {
+        var existing = Settings.FirstOrDefault(x => x.Key == key);
+
+        if (existing is null)
+        {
+            Settings.Add(new PlayerSetting(ProfileId, key, value));
+            return;
+        }
+
+        existing.UpdateValue(value);
+    }
+    
     private static string RequireValue(string value, string parameterName)
         => !string.IsNullOrWhiteSpace(value) ? value : throw new DomainException($"{parameterName} is required.");
 }