Fix issue with jwt decoding

lib/src/session/token.dart

@@ -179,7 +179,7 @@ Map<String, dynamic> getTenants(Map<String, dynamic> claims) {
 // JWT Decoding
 
 Uint8List decodeEncodedFragment(String value) {
-  final length = value.length + 4 - value.length % 4;
+  final length = 4 * ((value.length + 3) /  4).floor();
   final data = const Base64Decoder().convert(value.padRight(length, '='));
   return data;
 }

lib/src/types/others.dart

@@ -27,19 +27,6 @@ class SignUpDetails {
 
 /// Used to require additional behaviors when authenticating a user.
 class SignInOptions {
-  /// Adds additional custom claims to the user's JWT during authentication.
-  ///
-  /// For example, the following code starts an OTP sign in and requests a custom claim
-  /// with the authenticated user's full name:
-  ///
-  ///     try await descope.otp.signIn(with: .email, loginId: "andy@example.com", options: [
-  ///         .customClaims(["name": "{{user.name}}"]),
-  ///     ])
-  ///
-  /// - Important: Any custom claims added via this method are considered insecure and will
-  /// be nested under the `nsec` custom claim.
-  final Map<String, dynamic> customClaims;
-
   /// Used to add layered security to your app by implementing Step-up authentication.
   ///
   ///     final refreshJwt = Descope.sessionManager.session?.refreshJwt;
@@ -68,5 +55,18 @@ class SignInOptions {
   /// and refresh JWTs will be an array with an entry for each authentication method used.
   final String? mfaRefreshJwt;
 
-  const SignInOptions({this.customClaims = const {}, this.stepupRefreshJwt, this.mfaRefreshJwt});
+  /// Adds additional custom claims to the user's JWT during authentication.
+  ///
+  /// For example, the following code starts an OTP sign in and requests a custom claim
+  /// with the authenticated user's full name:
+  ///
+  ///     try await descope.otp.signIn(with: .email, loginId: "andy@example.com", options: [
+  ///         .customClaims(["name": "{{user.name}}"]),
+  ///     ])
+  ///
+  /// - Important: Any custom claims added via this method are considered insecure and will
+  /// be nested under the `nsec` custom claim.
+  final Map<String, dynamic> customClaims;
+
+  const SignInOptions({this.stepupRefreshJwt, this.mfaRefreshJwt, this.customClaims = const {}});
 }