Move files for better organization

src/Helpers/Utilities.cs

@@ -0,0 +1,38 @@
+
+using System;
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Text.RegularExpressions;
+
+namespace ReceiptPDFBuilders.Helpers;
+
+class Utilities
+{
+    public static JsonSerializerOptions GetSerializerOptions()
+    {
+        var opts = new JsonSerializerOptions 
+        { 
+            WriteIndented = false,
+            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+        };
+        return opts;
+    }
+
+    public static DateOnly? CheckValidDateInString(string str)
+    {
+        // https://stackoverflow.com/a/14918404/3938401
+        var rgx = new Regex(@"\d{4}-\d{2}-\d{2}");
+        var mat = rgx.Match(str);
+        if (mat.Success)
+        {
+            var dtStr = mat.ToString();
+            string[] formats = ["yyyy-MM-dd"];
+            DateTime parsedDateTime;
+            var didWork = DateTime.TryParseExact(dtStr, formats, CultureInfo.InvariantCulture,
+                                        DateTimeStyles.None, out parsedDateTime);
+            return didWork ? DateOnly.FromDateTime(parsedDateTime) : null;
+        }
+        return null;
+    }
+}