Refactor cookie handling and bump version to 1.0.1

Refactored `CookieNames.cs` to replace the `GetEnvelopeReceiverCookieName(string key)` method with new methods for extracting envelope receiver keys from cookie names:
- Added `GetEnvelopeReceiverKeyOrDefault` to extract keys or return `null` if the format is invalid.
- Added `TryGetEnvelopeReceiverKey` to attempt key extraction with a success flag.

Updated `DigitalData.Auth.Claims.csproj` to increment `Version`, `AssemblyVersion`, and `FileVersion` from 1.0.0 to 1.0.1, reflecting the new functionality.

DigitalData.Auth.Claims/CookieNames.cs

@@ -17,11 +17,30 @@ namespace DigitalData.Auth.Claims
             => defaultCookieName + ReceiverSuffix + key;
 
         /// <summary>
-        /// Builds the cookie name for an envelope receiver token. This overload assumes a default cookie name of "AuthToken".
+        /// Extracts the envelope receiver key from a cookie name, or returns <see langword="null"/> if the cookie name does not match the expected format.
         /// </summary>
-        /// <param name="key">The unique envelope receiver key.</param>
-        /// <returns>A cookie name in the format <c>{defaultCookieName}SignFLOWReceiver.{key}</c>.</returns>
-        public static string GetEnvelopeReceiverCookieName(string key)
-            => "AuthToken" + ReceiverSuffix + key;
+        /// <param name="cookieName">The full cookie name in the format <c>{defaultCookieName}SignFLOWReceiver.{key}</c>.</param>
+        /// <param name="defaultCookieName">The base cookie name configured in <c>AuthApiParams</c>.</param>
+        /// <returns>The envelope receiver key, or <see langword="null"/> if the cookie name does not match the expected format.</returns>
+        public static string? GetEnvelopeReceiverKeyOrDefault(string cookieName, string defaultCookieName)
+        {
+            var prefix = defaultCookieName + ReceiverSuffix;
+            return cookieName.StartsWith(prefix, StringComparison.Ordinal)
+                ? cookieName[prefix.Length..]
+                : null;
+        }
+
+        /// <summary>
+        /// Tries to extract the envelope receiver key from a cookie name.
+        /// </summary>
+        /// <param name="cookieName">The full cookie name in the format <c>{defaultCookieName}SignFLOWReceiver.{key}</c>.</param>
+        /// <param name="defaultCookieName">The base cookie name configured in <c>AuthApiParams</c>.</param>
+        /// <param name="key">The extracted envelope receiver key if the cookie name matches the expected format; otherwise <see langword="null"/>.</param>
+        /// <returns><see langword="true"/> if the key was successfully extracted; otherwise <see langword="false"/>.</returns>
+        public static bool TryGetEnvelopeReceiverKey(string cookieName, string defaultCookieName, out string? key)
+        {
+            key = GetEnvelopeReceiverKeyOrDefault(cookieName, defaultCookieName);
+            return key is not null;
+        }
     }
 }