feat: add identity_file field to config connections config

internal/cli/config/connection.go

@@ -14,10 +14,11 @@ const (
 )
 
 type MachineConnection struct {
-	SSH       SSHDestination `toml:"ssh,omitempty"`
-	TCP       netip.AddrPort `toml:"tcp,omitempty"`
-	Host      string         `toml:"host,omitempty"`
-	PublicKey secret.Secret  `toml:"public_key,omitempty"`
+	SSH          SSHDestination `toml:"ssh,omitempty"`
+	TCP          netip.AddrPort `toml:"tcp,omitempty"`
+	Host         string         `toml:"host,omitempty"`
+	PublicKey    secret.Secret  `toml:"public_key,omitempty"`
+	IdentityFile string         `toml:"identity_file,omitempty"`
 }
 
 // SSHDestination represents an SSH destination string in the canonical form of "user@host:port".