all: refactor router code to use interface

So the code is more modular, easier to read/maintain.

internal/router/dummy.go

@@ -0,0 +1,37 @@
+package router
+
+import "github.com/kardianos/service"
+
+type dummy struct{}
+
+func NewDummyRouter() Router {
+	return &dummy{}
+}
+
+func (d *dummy) ConfigureService(_ *service.Config) error {
+	return nil
+}
+
+func (d *dummy) Install(_ *service.Config) error {
+	return nil
+}
+
+func (d *dummy) Uninstall(_ *service.Config) error {
+	return nil
+}
+
+func (d *dummy) PreRun() error {
+	return nil
+}
+
+func (d *dummy) Configure() error {
+	return nil
+}
+
+func (d *dummy) Setup() error {
+	return nil
+}
+
+func (d *dummy) Cleanup() error {
+	return nil
+}