Add option to configure tolerations in kubernetes backend (#2249)

This code add a feature to support tolerations in Kubernetes Backend

---------

Signed-off-by: Kleber Rocha <klinux@gmail.com>

pipeline/backend/kubernetes/pod.go

@@ -125,6 +125,22 @@ func Pod(namespace string, step *types.Step, labels, annotations map[string]stri
 		}
 	}
 
+	var tolerations []v1.Toleration
+	beTolerations := step.BackendOptions.Kubernetes.Tolerations
+	if len(beTolerations) > 0 {
+		for _, t := range step.BackendOptions.Kubernetes.Tolerations {
+			toleration := v1.Toleration{
+				Key:               t.Key,
+				Operator:          v1.TolerationOperator(t.Operator),
+				Value:             t.Value,
+				Effect:            v1.TaintEffect(t.Effect),
+				TolerationSeconds: t.TolerationSeconds,
+			}
+			tolerations = append(tolerations, toleration)
+		}
+		log.Trace().Msgf("Tolerations that will be used in the backend options: %v", beTolerations)
+	}
+
 	pod := &v1.Pod{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:        podName,
@@ -136,6 +152,7 @@ func Pod(namespace string, step *types.Step, labels, annotations map[string]stri
 			RestartPolicy:      v1.RestartPolicyNever,
 			HostAliases:        hostAliases,
 			NodeSelector:       nodeSelector,
+			Tolerations:        tolerations,
 			ServiceAccountName: serviceAccountName,
 			Containers: []v1.Container{{
 				Name:            podName,