* Add gocritic linter
`gocritic` provides diagnostics that check for bugs, performance, and style issues
We disable the following checks:
- commentFormatting
- captLocal
- deprecatedComment
This PR contains many `//nolint:gocritic` to disable `appendAssign`.
* shutdown the pkce server on user cancellation
* Refactor openURL to exclusively manage authentication flow instructions and browser launching
* Refactor authentication flow initialization based on client OS
The NewOAuthFlow method now first checks the operating system and if it is a non-desktop Linux, it opts for Device Code Flow. PKCEFlow is tried first and if it fails, then it falls back on Device Code Flow. If both unsuccessful, the authentication process halts and error messages have been updated to provide more helpful feedback for troubleshooting authentication errors
* Replace log-based Linux desktop check with process check
To verify if a Linux OS is running a desktop environment in the Authentication utility, the log-based method that checks the XDG_CURRENT_DESKTOP env has been replaced with a method that checks directly if either X or Wayland display server processes are running. This method is more reliable as it directly checks for the display server process rather than relying on an environment variable that may not be set in all desktop environments.
* Refactor PKCE Authorization Flow to improve server handling
* refactor check for linux running desktop environment
* Improve server shutdown handling and encapsulate handlers with new server multiplexer
The changes enhance the way the server shuts down by specifying a context with timeout of 5 seconds, adding a safeguard to ensure the server halts even on potential hanging requests. Also, the server's root handler is now encapsulated within a new ServeMux instance, to support multiple registrations of a path
Switches the order of initialization in the OAuth flow within
the NewOAuthFlow method. Instead of initializing the
Device Authorization Flow first, it now initializes
the PKCE Authorization Flow first, and falls back
to the Device Authorization Flow if the PKCE initialization fails.
Enhance the user experience by enabling authentication to Netbird using Single Sign-On (SSO) with any Identity Provider (IDP) provider. Current client offers this capability through the Device Authorization Flow, however, is not widely supported by many IDPs, and even some that do support it do not provide a complete verification URL.
To address these challenges, this pull request enable Authorization Code Flow with Proof Key for Code Exchange (PKCE) for client logins, which is a more widely adopted and secure approach to facilitate SSO with various IDP providers.
