Add avatar support

src/RecNet.Domain/Profiles/Profile.cs

@@ -35,6 +35,8 @@ public class Profile
 
     public DateTimeOffset CreatedAt { get; private set; }
 
+    public Avatar Avatar { get; private set; } = Avatar.Empty;
+
     public static Profile Create(
         string name, 
         PlatformType platform, 
@@ -81,6 +83,9 @@ public class Profile
     public void RevokeModerator()
         => IsModerator = false;
     
+    public void SetAvatar(Avatar avatar)
+        => Avatar = avatar ?? throw new DomainException("Avatar is required.");
+    
     private static string RequireValue(string value, string parameterName)
         => !string.IsNullOrWhiteSpace(value) ? value : throw new DomainException($"{parameterName} is required.");
 }