pam-moduler: Add test that generates a new debug module and verify it works

We mimic what pam_debug.so does by default, by implementing a similar
module fully in go, generated using pam-moduler.

This requires various utilities to generate the module and run the tests
that are in a separate internal modules so that it can be shared between
multiple implementations

cmd/pam-moduler/tests/internal/utils/test-utils.go

@@ -0,0 +1,99 @@
+// Package utils contains the internal test utils
+package utils
+
+// Action represents a PAM action to perform.
+type Action int
+
+const (
+	// Account is the account.
+	Account Action = iota + 1
+	// Auth is the auth.
+	Auth
+	// Password is the password.
+	Password
+	// Session is the session.
+	Session
+)
+
+func (a Action) String() string {
+	switch a {
+	case Account:
+		return "account"
+	case Auth:
+		return "auth"
+	case Password:
+		return "password"
+	case Session:
+		return "session"
+	default:
+		return ""
+	}
+}
+
+// Actions is a map with all the available Actions by their name.
+var Actions = map[string]Action{
+	Account.String():  Account,
+	Auth.String():     Auth,
+	Password.String(): Password,
+	Session.String():  Session,
+}
+
+// Control represents how a PAM module should controlled in PAM service file.
+type Control int
+
+const (
+	// Required implies that the module is required.
+	Required Control = iota + 1
+	// Requisite implies that the module is requisite.
+	Requisite
+	// Sufficient implies that the module is sufficient.
+	Sufficient
+	// Optional implies that the module is optional.
+	Optional
+)
+
+func (c Control) String() string {
+	switch c {
+	case Required:
+		return "required"
+	case Requisite:
+		return "requisite"
+	case Sufficient:
+		return "sufficient"
+	case Optional:
+		return "optional"
+	default:
+		return ""
+	}
+}
+
+// ServiceLine is the representation of a PAM module service file line.
+type ServiceLine struct {
+	Action  Action
+	Control Control
+	Module  string
+	Args    []string
+}
+
+// FallBackModule is a type to represent the module that should be used as fallback.
+type FallBackModule int
+
+const (
+	// NoFallback add no fallback module.
+	NoFallback FallBackModule = iota + 1
+	// Permit uses a module that always permits.
+	Permit
+	// Deny uses a module that always denys.
+	Deny
+)
+
+func (a FallBackModule) String() string {
+	switch a {
+	case Permit:
+		return "pam_permit.so"
+	case Deny:
+		return "pam_deny.so"
+	default:
+		return ""
+	}
+}