Classify missing expected router %s as user error

[Kostov6]

How to categorize this issue?

/area quality
/kind enhancement
/platform openstack

What would you like to be added:

gardener-extension-provider-openstack/pkg/controller/infrastructure/infraflow/reconcile.go

Lines 115 to 124 in a08ed29

	router, err := fctx.access.GetRouterByID(fctx.config.Networks.Router.ID)
	if err != nil {
	fctx.state.Set(IdentifierRouter, "")
	fctx.state.Set(RouterIP, "")
	return err
	}
	if router == nil {
	fctx.state.Set(IdentifierRouter, "")
	fctx.state.Set(RouterIP, "")
	return fmt.Errorf("missing expected router %s", fctx.config.Networks.Router.ID)

Could be tagged as user error

Why is this needed:
Improved error classification

[Kostov6]

/assign Kostov6