v2.1.0

Minor release changes

• Add additional init to HTTPError that takes list of headers. Also remove the assumption that HTTPError content-type is json. #561

Patch release changes

• Remove @escaping from Application.test closure. #555
• Environment.set will actually set the environment variable. #557
• Remove retroactive Sendable requirement from JSONEncoder/Decoder. #559
• Don't update expires value if persist update is called with nil expire value. #562
• Check for HTTPResponseError instead of HTTPError in FileMiddleware. #569
• Use ProcessInfo.processInfo.environment instead of environ. #571 from @GNMoseke

Other changes

• Add GitHub action for verifying documentation headers. #554
• Add Swift 6 to GitHub CI. #556