shim: user switcher process management struct

This change moves all user switcher and shim management to the shim package and withholds output while shim is alive. This also eliminated all exit scenarios where revert is skipped.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/app/app.go

@@ -1,10 +1,10 @@
 package app
 
 import (
-	"os/exec"
 	"sync"
 
 	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/shim"
 )
 
 type App interface {
@@ -26,10 +26,8 @@ type app struct {
 	id *ID
 	// operating system interface
 	os internal.System
-	// underlying user switcher process
-	cmd *exec.Cmd
-	// shim setup abort reason and completion
-	abort chan error
+	// shim process manager
+	shim *shim.Shim
 	// child process related information
 	seal *appSeal
 	// error returned waiting for process
@@ -50,8 +48,8 @@ func (a *app) String() string {
 	a.lock.RLock()
 	defer a.lock.RUnlock()
 
-	if a.cmd != nil {
-		return a.cmd.String()
+	if a.shim != nil {
+		return a.shim.String()
 	}
 
 	if a.seal != nil {