add a bunch of authentication stuff

Foxchat.Core/Utils/ConvertUtils.cs

@@ -0,0 +1,23 @@
+using System.Security.Cryptography;
+
+namespace Foxchat.Core.Utils;
+
+public static class CryptoUtils
+{
+    public static bool TryFromBase64String(string b64, out byte[] bytes)
+    {
+        try
+        {
+            bytes = Convert.FromBase64String(b64);
+            return true;
+        }
+        catch
+        {
+            bytes = [];
+            return false;
+        }
+    }
+
+    public static string RandomToken(int bytes = 48) =>
+        Convert.ToBase64String(RandomNumberGenerator.GetBytes(bytes)).Trim('=');
+}