Release v9.2.0

Changes:

• Slim down the default request context to headers, ip and library; the remaining data is already available via headers.
• Remove the internal Castle::ClientId::Extract service and the now-unused cookies plumbing in Castle::Context::GetDefault.
• No longer read the API secret from the CASTLE_API_SECRET environment variable automatically; set Castle.api_secret explicitly (for example Castle.api_secret = ENV.fetch('CASTLE_API_SECRET')).