Adding initial version of Kubernetes backend (#552)

Co-authored-by: laszlocph <laszlo@laszlo.cloud>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Rynoxx <rynoxx@grid-servers.net>

pipeline/backend/kubernetes/service_test.go

@@ -0,0 +1,47 @@
+package kubernetes
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestService(t *testing.T) {
+	expected := `
+	{
+	  "metadata": {
+	    "name": "bar",
+	    "namespace": "foo",
+	    "creationTimestamp": null
+	  },
+	  "spec": {
+	    "ports": [
+	      {
+	        "port": 1,
+	        "targetPort": 1
+	      },
+	      {
+	        "port": 2,
+	        "targetPort": 2
+	      },
+	      {
+	        "port": 3,
+	        "targetPort": 3
+	      }
+	    ],
+	    "selector": {
+	      "step": "baz"
+	    },
+	    "type": "ClusterIP"
+	  },
+	  "status": {
+	    "loadBalancer": {}
+	  }
+	}`
+
+	s, _ := Service("foo", "bar", "baz", []string{"1", "2", "3"})
+	j, err := json.Marshal(s)
+	assert.Nil(t, err)
+	assert.JSONEq(t, expected, string(j))
+}