chore: add alb ingress controller docs run-it-locally how-to

Author: Kamil Przybyl

docs/ingress-controller.md

@@ -0,0 +1,103 @@
+### Run the ALB Ingress controller locally
+To run the controller on your local machine, ensure you have a valid kubeconfig pointing to the target Kubernetes cluster where the ALB resources should be managed.
+
+##### Environment Variables
+The controller requires specific configuration and credentials to interact with the STACKIT APIs and your network infrastructure. Set the following variables:
+  - STACKIT_SERVICE_ACCOUNT_TOKEN: Your authentication token for performing CRUD operations via the ALB and Certificates SDK.
+  - STACKIT_REGION: The STACKIT region where the infrastructure resides (e.g., eu01).
+  - PROJECT_ID: The unique identifier of your STACKIT project where the ALB will be provisioned.
+  - NETWORK_ID: The ID of the STACKIT network where the ALB will be provisioned.
+```
+export STACKIT_SERVICE_ACCOUNT_TOKEN=<your-token>
+export STACKIT_REGION=<region>
+export PROJECT_ID=<project-id>
+export NETWORK_ID=<network-id>
+```
+Kubernetes Context
+The controller uses the default Kubernetes client. Ensure your KUBECONFIG environment variable is set or your current context is correctly configured:
+```
+export KUBECONFIG=~/.kube/config
+```
+#### Run
+Use the provided Makefile in the root of repository to start the controller:
+```
+make run
+```
+
+### Create your deployment and expose it via Ingress
+1. Create your k8s deployment, here’s an example of a simple http web server:
+```
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: httpbin-deployment
+  name: httpbin-deployment
+  namespace: default
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app: httpbin-deployment
+  template:
+    metadata:
+      labels:
+        app: httpbin-deployment
+    spec:
+      containers:
+      - image: kennethreitz/httpbin
+        name: httpbin
+        ports:
+        - containerPort: 80
+```
+2. Now, create a k8s service so that the traffic can be routed to the pods:
+```
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app: httpbin-deployment
+  name: httpbin
+  namespace: default
+spec:
+  ports:
+  - port: 80
+    protocol: TCP
+    targetPort: 80
+    nodePort: 30000
+  selector:
+    app: httpbin-deployment
+  type: NodePort
+```
+>NOTE: The service has to be of type NodePort to enable access to the nodes from the outside of the cluster.
+3. Create an IngressClass that specifies the ALB Ingress controller:
+```
+apiVersion: networking.k8s.io/v1
+kind: IngressClass
+metadata:
+  namespace: default
+  name: alb-01
+spec:
+  controller: stackit.cloud/alb-ingress
+```
+4. Lastly, create an ingress resource that references the previously created IngressClass:
+```
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: alb-ingress
+  namespace: default
+spec:
+  ingressClassName: alb-01
+  rules:
+  - host: example.gg
+    http:
+      paths:
+      - path: /
+        pathType: Prefix
+        backend:
+          service:
+            name: httpbin
+            port:
+              number: 80
+```