add readme section

Author: reshnm

README.md

@@ -298,6 +298,82 @@ env := testing.NewEnvironmentBuilder().
 env.ShouldReconcile(testing.RequestFromStrings("testresource"))
 ```
 
+### Kubernetes resource management
+
+The `pkg/resource` package contains some useful functions for working with Kubernetes resources. The `Mutator` interface can be used to modify resources in a generic way. It is used by the `Mutate` function, which takes a resource and a mutator and applies the mutator to the resource.
+The package also contains convenience types for the most common resource types, e.g. `ConfigMap`, `Secret`, `ClusterRole`, `ClusterRoleBinding`, etc. These types implement the `Mutator` interface and can be used to modify the corresponding resources.
+
+#### Examples
+
+Create or update a `ConfigMap`, a `ServiceAccount` and a `Deployment` using the `Mutator` interface:
+
+```go
+type myDeploymentMutator struct {
+}
+
+var _ resource.Mutator[*appsv1.Deployment] = &myDeploymentMutator{}
+
+func newDeploymentMutator() resources.Mutator[*appsv1.Deployment] {
+	return &MyDeploymentMutator{}
+}
+
+func (m *MyDeploymentMutator) String() string {
+	return "deployment default/test"
+}
+
+func (m *MyDeploymentMutator) Empty() *appsv1.Deployment {
+	return &appsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{	
+			Name:      "test",
+			Namespace: "default",
+		},
+	}
+}
+
+func (m *MyDeploymentMutator) Mutate(deployment *appsv1.Deployment) error {
+	// create one container with an image
+	deployment.Spec.Template.Spec.Containers = []corev1.Container{
+		{
+			Name:  "test",
+			Image: "test-image:latest",
+		},
+	}
+	return nil
+}
+
+
+func ReconcileResources(ctx context.Context, client client.Client) error {
+	configMapResource := resource.NewConfigMap("my-configmap", "my-namespace", map[string]string{)
+		"label1": "value1",
+		"label2": "value2",
+	}, nil)
+
+	serviceAccountResource := resource.NewServiceAccount("my-serviceaccount", "my-namespace", nil, nil)
+	
+	myDeploymentMutator := newDeploymentMutator()
+	
+	var err error
+	
+	err = resources.CreateOrUpdateResource(ctx, client, configMapResource)
+	if err != nil {
+		return err
+	}
+	
+	resources.CreateOrUpdateResource(ctx, client, serviceAccountResource)
+	if err != nil {
+		return err
+	}
+	
+	err = resources.CreateOrUpdateResource(ctx, client, myDeploymentMutator)
+	if err != nil {
+		return err
+	}
+	
+	return nil
+}
+
+```
+
 ## Support, Feedback, Contributing
 
 This project is open to feature requests/suggestions, bug reports etc. via [GitHub issues](https://github.com/openmcp-project/controller-utils/issues). Contribution and feedback are encouraged and always welcome. For more information about how to contribute, the project structure, as well as additional contribution information, see our [Contribution Guidelines](CONTRIBUTING.md).