add networkd test apply logic

internal/networkd/apply.go

@@ -0,0 +1,33 @@
+package networkd
+
+import (
+	"fmt"
+	"os"
+
+	"nfsense.net/nfsense/internal/definitions"
+)
+
+func ApplyNetworkdConfiguration(currentConfig definitions.Config, pendingConfig definitions.Config) error {
+	files, err := GenerateNetworkdConfiguration(pendingConfig)
+	if err != nil {
+		return fmt.Errorf("Generating Networkd Configuration: %w", err)
+	}
+
+	for _, file := range files {
+		f, err := os.Create("out/" + file.Name)
+		if err != nil {
+			return fmt.Errorf("creating File: %w", err)
+		}
+
+		_, err = f.WriteString(file.Content + "\n")
+		if err != nil {
+			return fmt.Errorf("writing File: %w", err)
+		}
+
+		err = f.Sync()
+		if err != nil {
+			return fmt.Errorf("syncing File: %w", err)
+		}
+	}
+	return nil
+}