chore: remove some duplication and add a first few tests

cmd/handler/handler.go

@@ -28,7 +28,7 @@ func main() {
 	if kubecfg, exists := os.LookupEnv("KUBECONFIG"); exists {
 		kubeClient = kube.New(kube.WithKubeConfigProvider(kubecfg))
 	} else {
-		kubeClient = kube.New(kube.WithInClusterProvider())
+		kubeClient = kube.New()
 	}
 	gitlabClient := gitlab.New(cli.GitlabToken)
 	if err := handle(cli, logger, kubeClient, gitlabClient); err != nil {