Fix launcher not showing mods

Convert `Version` and `SptVersion` to strings when serializing JSON for AbstractModMetadata

Libraries/SPTarkov.Server.Core/Models/Spt/Mod/AbstractModMetadata.cs

@@ -1,4 +1,6 @@
-using Range = SemanticVersioning.Range;
+using System.Text.Json.Serialization;
+using SPTarkov.Server.Core.Utils.Json.Converters;
+using Range = SemanticVersioning.Range;
 using Version = SemanticVersioning.Version;
 
 namespace SPTarkov.Server.Core.Models.Spt.Mod;
@@ -40,6 +42,7 @@ public abstract record AbstractModMetadata
     /// <br/>
     /// Version = new Version("1.0.0.0"); is not
     /// </summary>
+    [JsonConverter(typeof(ToStringJsonConverter<Version>))]
     public abstract Version Version { get; init; }
 
     /// <summary>
@@ -49,6 +52,7 @@ public abstract record AbstractModMetadata
     /// <br/>
     /// Version = new Version("4.0.0.0"); is not
     /// </summary>
+    [JsonConverter(typeof(ToStringJsonConverter<Range>))]
     public abstract Range SptVersion { get; init; }
 
     /// <summary>

Libraries/SPTarkov.Server.Core/Utils/Json/Converters/ToStringJsonConverter.cs

@@ -0,0 +1,24 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace SPTarkov.Server.Core.Utils.Json.Converters;
+
+internal class ToStringJsonConverter<T> : JsonConverter<T>
+{
+    public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        throw new NotSupportedException($"Deserialization of {typeof(T).Name} from string is not supported.");
+    }
+
+    public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+    {
+        if (value == null)
+        {
+            writer.WriteNullValue();
+        }
+        else
+        {
+            writer.WriteStringValue(value.ToString());
+        }
+    }
+}