Add code to format disk as ext4 in guest

internal/guest/storage/ext4/format.go

@@ -0,0 +1,27 @@
+//go:build linux
+// +build linux
+
+package ext4
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+)
+
+// mkfsExt4Command runs mkfs.ext4 with the provided arguments
+func mkfsExt4Command(args []string) error {
+	cmd := exec.Command("mkfs.ext4", args...)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("failed to execute mkfs.ext4: %s: %w", string(output), err)
+	}
+	return nil
+}
+func FormatExt4(ctx context.Context, source string) error {
+	// Format source as ext4
+	if err := mkfsExt4Command([]string{source}); err != nil {
+		return fmt.Errorf("mkfs.ext4 failed to format %s: %w", source, err)
+	}
+	return nil
+}