Add Meta authentication secret and SHA256 hashing

src/RecNet.Application/Common/Security/Hashing.cs

@@ -0,0 +1,19 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace RecNet.Application.Common.Security;
+
+public static class Hashing
+{
+    public static byte[] ComputeSha256(string input)
+        => SHA256.HashData(Encoding.UTF8.GetBytes(input));
+
+    public static bool VerifySha256(string input, byte[] expectedHash)
+    {
+        var computedHash = ComputeSha256(input);
+
+        return CryptographicOperations.FixedTimeEquals(
+            computedHash,
+            expectedHash);
+    }
+}