I’m also going to echo @alexmurray’s concerns and vote -1 for auto-connection.
Others have provided excellent advice and I’ll reiterate that your snap is free to plugs ‘ssh-keys’ without auto-connection and say your snap is in a position to snapctl is_connected ssh-keys to see if the interface is connected which gives your snap an opportunity to guide the user to connect. A cli experience could exit early if they invoke using ssh and a gui experience could provide a warning stating what to do if the user invokes the ssh feature.
There are also plans to provide APIs for snaps to use that would allow a snap to trigger the connection prompt themselves.