Quickly switch between Tailscale accounts

Tailscale's v1.34 update introduces fast user switching, allowing users to seamlessly switch between different Tailscale accounts on the same device without the need for re-authentication, enhancing convenience for those using Tailscale in both personal and professional contexts. This feature is available in alpha on Linux, macOS, and Windows, with support for additional platforms planned for the future. Users can switch accounts by selecting them from the menu on macOS or using terminal commands, and they can assign nicknames to accounts for even easier switching. Fast user switching ensures that each identity remains separate, with no communication between different tailnets, though re-authentication is required if the device's node key expires.