Replace pistache solar-server with .net solar api

src/Solar.Api/Converters/DateOnlyConverter.cs

@@ -0,0 +1,24 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Solar.Api.Converters;
+
+public class DateOnlyConverter : JsonConverter<DateOnly>
+{
+    private const string serializationFormat = "yyyy-MM-dd";
+
+    public override DateOnly Read(
+        ref Utf8JsonReader reader,
+        Type typeToConvert,
+        JsonSerializerOptions options)
+    {
+        var value = reader.GetString();
+        return DateOnly.ParseExact(value!, serializationFormat);
+    }
+
+    public override void Write(
+        Utf8JsonWriter writer,
+        DateOnly value,
+        JsonSerializerOptions options)
+        => writer.WriteStringValue(value.ToString(serializationFormat));
+}