feat(code_push_client): add CodePushUpgradeRequiredException (#655)

packages/shorebird_code_push_client/lib/src/code_push_client.dart

@@ -38,6 +38,17 @@ class CodePushNotFoundException extends CodePushException {
   CodePushNotFoundException({required super.message, super.details});
 }
 
+/// {@template code_push_upgrade_required_exception}
+/// Exception thrown when a 426 response is received.
+/// {@endtemplate}
+class CodePushUpgradeRequiredException extends CodePushException {
+  /// {@macro code_push_upgrade_required_exception}
+  const CodePushUpgradeRequiredException({
+    required super.message,
+    super.details,
+  });
+}
+
 /// A wrapper around [http.Client] that ensures all outbound requests
 /// are consistent.
 /// For example, all requests include the standard `x-version` header.
@@ -466,6 +477,7 @@ class CodePushClient {
     final exceptionBuilder = switch (statusCode) {
       HttpStatus.conflict => CodePushConflictException.new,
       HttpStatus.notFound => CodePushNotFoundException.new,
+      HttpStatus.upgradeRequired => CodePushUpgradeRequiredException.new,
       _ => CodePushException.new,
     };
 

packages/shorebird_code_push_client/test/src/code_push_client_test.dart

@@ -60,6 +60,20 @@ void main() {
       });
     });
 
+    test('throws CodePushUpgradeRequiredException on 426 response', () async {
+      when(() => httpClient.send(any())).thenAnswer(
+        (_) async => http.StreamedResponse(
+          Stream.empty(),
+          HttpStatus.upgradeRequired,
+        ),
+      );
+
+      expect(
+        codePushClient.getApps(),
+        throwsA(isA<CodePushUpgradeRequiredException>()),
+      );
+    });
+
     group('createCollaborator', () {
       const appId = 'test-app-id';
       const email = 'jane.doe@shorebird.dev';