docs: add Kustomize instructions to README

Signed-off-by: Mark Sagi-Kazar <[email protected]>

README.md

@@ -10,9 +10,10 @@ Redis Operator creates/configures/manages redis-failovers atop Kubernetes.
 Redis Operator is meant to be run on Kubernetes 1.19+.
 All dependencies have been vendored, so there's no need to any additional download.
 
-## Operator deployment on kubernetes
+## Operator deployment on Kubernetes
 
-In order to create Redis failovers inside a Kubernetes cluster, the operator has to be deployed. It can be done with [deployment](example/operator) or with the provided [Helm chart](charts/redisoperator).
+In order to create Redis failovers inside a Kubernetes cluster, the operator has to be deployed.
+It can be done with plain old [deployment](example/operator), using [Kustomize](manifests/kustomize) or with the provided [Helm chart](charts/redisoperator).
 
 ### Using the Helm chart
 
@@ -46,6 +47,45 @@ kubectl apply -f https://raw.githubusercontent.com/spotahome/redis-operator/mast
 
 This will create a deployment named `redisoperator`.
 
+### Using kustomize
+
+The kustomize setup included in this repo is highly customizable using [components](https://kubectl.docs.kubernetes.io/guides/config_management/components/),
+but it also comes with a few presets (in the form of overlays) supporting the most common use cases.
+
+To install the operator with default settings and every necessary resource (including RBAC, service account, default resource limits, etc), install the `default` overlay:
+
+```shell
+kustomize build github.com/spotahome/redis-operator/manifests/kustomize/overlays/default
+```
+
+If you would like to customize RBAC or the service account used, you can install the `minimal` overlay.
+
+Finally, you can install the `full` overlay if you want everything this operator has to offer, including Prometheus ServiceMonitor resources.
+
+It's always a good practice to pin the version of the operator in your configuration to make sure you are not surprised by changes on the latest development branch:
+
+```shell
+kustomize build github.com/spotahome/redis-operator/manifests/kustomize/overlays/default?ref=v1.2.0
+```
+
+You can easily create your own config by creating a `kustomization.yaml` file
+(for example to apply custom resource limits, to add custom labels or to customize the namespace):
+
+```yaml
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: redis-operator
+
+commonLabels:
+    foo: bar
+
+resources:
+  - github.com/spotahome/redis-operator/manifests/kustomize/overlays/full
+```
+
+Take a look at the manifests inside [manifests/kustomize](manifests/kustomize) for more details.
+
 ## Usage
 
 Once the operator is deployed inside a Kubernetes cluster, a new API will be accesible, so you'll be able to create, update and delete redisfailovers.