docs: document empty/whitespace passthrough behavior in ICryptoProvider

src/StevanFreeborn.Extensions.Configuration.Secure/Cryptography/ICryptoProvider.cs

@@ -9,13 +9,13 @@ public interface ICryptoProvider
   /// Encrypts the provided plain text.
   /// </summary>
   /// <param name="plainText">The unencrypted string to be encrypted.</param>
-  /// <returns>The encrypted cipher text.</returns>
+  /// <returns>The encrypted cipher text. If <paramref name="plainText"/> is null, empty, or whitespace, it is returned unchanged.</returns>
   string Encrypt(string plainText);
 
   /// <summary>
   /// Decrypts the provided cipher text.
   /// </summary>
   /// <param name="cipherText">The encrypted string to be decrypted.</param>
-  /// <returns>The decrypted plain text.</returns>
+  /// <returns>The decrypted plain text. If <paramref name="cipherText"/> is null, empty, or whitespace, it is returned unchanged.</returns>
   string Decrypt(string cipherText);
 }