convert Pilz to c# & add AppVersion to there

Pilz/Json/AppVersionStringJsonConverter.cs

@@ -0,0 +1,80 @@
+using Newtonsoft.Json;
+
+namespace Pilz.Json;
+
+public class AppVersionStringJsonConverter(bool serializeAsObject) : JsonConverter
+{
+    public AppVersionStringJsonConverter() : this(false)
+    {
+    }
+
+    /// <summary>
+    /// Writes the JSON representation of the object.
+    /// </summary>
+    /// <param name="writer">The <see cref="JsonWriter"/> to write to.</param>
+    /// <param name="value">The value.</param>
+    /// <param name="serializer">The calling serializer.</param>
+    public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
+    {
+        if (value == null)
+        {
+            writer.WriteNull();
+            return;
+        }
+
+        if (serializeAsObject || value is not AppVersion appVersion)
+            writer.WriteValue(value);
+        else
+            writer.WriteValue(appVersion.ToString());
+    }
+
+    /// <summary>
+    /// Reads the JSON representation of the object.
+    /// </summary>
+    /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
+    /// <param name="objectType">Type of the object.</param>
+    /// <param name="existingValue">The existing value of object being read.</param>
+    /// <param name="serializer">The calling serializer.</param>
+    /// <returns>The object value.</returns>
+    public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
+    {
+        if (reader.TokenType == JsonToken.Null)
+            return null;
+
+        try
+        {
+            if (reader.TokenType == JsonToken.String)
+            {
+                var strValue = reader.Value?.ToString();
+
+                if (string.IsNullOrWhiteSpace(strValue))
+                    return null;
+
+                return AppVersion.Parse(strValue);
+
+            }
+
+            if (reader.TokenType == JsonToken.StartObject)
+                return serializer.Deserialize<AppVersion>(reader);
+        }
+        catch (Exception ex)
+        {
+            throw new JsonSerializationException("Error converting value {0} to type '{1}'.", ex);
+        }
+
+        // we don't actually expect to get here.
+        throw new JsonSerializationException("Unexpected token {0} when parsing app version.");
+    }
+
+    /// <summary>
+    /// Determines whether this instance can convert the specified object type.
+    /// </summary>
+    /// <param name="objectType">Type of the object.</param>
+    /// <returns>
+    /// <c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
+    /// </returns>
+    public override bool CanConvert(Type objectType)
+    {
+        return objectType == typeof(AppVersion);
+    }
+}