Refactor SSH prefix into a workspace suffix

[ThomasK33]

To implement one-click buttons for native applications in Coder Desktop, we need to refactor how (SSH) hostnames are handled⁠.

Currently, Coder uses a hostname prefix for SSH configuration, but this approach is incompatible with Coder Desktop which requires a suffix-based approach. This refactoring is necessary to enable seamless deep linking and native application launches⁠⁠.

Tasks include:

• Deprecate the existing hostname prefix option⁠⁠
• Implement a new hostname suffix option to be used by the config-ssh command and Coder Desktop (e.g., HostnameSuffix, defaulting to coder)⁠
• Update the config-ssh subcommand to reflect these changes⁠⁠
• Dynamically configure VPN DNS settings & workspace hostnames based on the hostname suffix

[aaronlehmann]

Are you planning to change the IDE plugins to use a suffix rather than a prefix?

[ThomasK33]

Are you planning to change the IDE plugins to use a suffix rather than a prefix?

Hey @aaronlehmann 👋 , yes, we will update the plugins to use the suffix and make them aware of the existing Coder Desktop tunnel.

Just a heads up, those changes will come in a later phase, so keep an eye on the parent issue (phase 1) for more info.

[deansheather]

Since this needs to be used by the UI, the extensions and the desktop apps, it will most likely need to be a server-side option for consistency