Align curated assets model with XUMM-SDK (#34)

Author: DominiqueBlomsma

src/XUMM.NET.SDK/Models/Misc/XummCuratedAssetsDetails.cs

@@ -12,10 +12,10 @@ public class XummCuratedAssetsDetails
     public string Name { get; set; } = default!;
 
     [JsonPropertyName("domain")]
-    public string Domain { get; set; } = default!;
+    public string? Domain { get; set; }
 
     [JsonPropertyName("avatar")]
-    public string Avatar { get; set; } = default!;
+    public string? Avatar { get; set; }
 
     [JsonPropertyName("shortlist")]
     public int Shortlist { get; set; }

src/XUMM.NET.SDK/Models/Misc/XummCuratedAssetsDetailsCurrency.cs

@@ -26,7 +26,7 @@ public class XummCuratedAssetsDetailsCurrency
     public string Name { get; set; } = default!;
 
     [JsonPropertyName("avatar")]
-    public string Avatar { get; set; } = default!;
+    public string? Avatar { get; set; }
 
     [JsonPropertyName("shortlist")]
     public int Shortlist { get; set; }