Use keyfiles

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/jupiter-vps/configs/wireguard/default.nix

@@ -31,7 +31,7 @@ in
             "10.0.0.2/32"
             "${jupiterPublicIPv4}/32"
           ];
-          publicKey = "l0V4syZrk7HkGNa7l0cq1a4taJcdo8nKGuZt9sq3FgE=";
+          publicKey = builtins.readFile "${inputs.secrets}/hosts/jupiter/wireguard_key.pub";
         }
       ];
     };