Add annotation to customize nginx location configuration

examples/customization/configuration-snippets/nginx/README.md

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+# Deploying the Nginx Ingress controller
+
+This example aims to demonstrate the deployment of an nginx ingress controller and
+with the use of an annotation in the Ingress rule be able to customize the nginx 
+configuration.
+
+## Default Backend
+
+The default backend is a Service capable of handling all url paths and hosts the
+nginx controller doesn't understand. This most basic implementation just returns
+a 404 page:
+
+```console
+$ kubectl apply -f default-backend.yaml
+deployment "default-http-backend" created
+service "default-http-backend" created
+
+$ kubectl -n kube-system get po
+NAME                                    READY     STATUS    RESTARTS   AGE
+default-http-backend-2657704409-qgwdd   1/1       Running   0          28s
+```
+
+```console
+$ kubectl create -f nginx-load-balancer-conf.yaml
+```
+
+## Controller
+
+You can deploy the controller as follows:
+
+```console
+$ kubectl apply -f nginx-ingress-controller.yaml
+deployment "nginx-ingress-controller" created
+
+$ kubectl -n kube-system get po
+NAME                                       READY     STATUS    RESTARTS   AGE
+default-http-backend-2657704409-qgwdd      1/1       Running   0          2m
+nginx-ingress-controller-873061567-4n3k2   1/1       Running   0          42s
+```
+
+## Test
+
+Check the contents of the annotation is present in the nginx.conf file using:
+`kubectl exec nginx-ingress-controller-873061567-4n3k2 -n kube-system cat /etc/nginx/nginx.conf`

examples/customization/configuration-snippets/nginx/default-backend.yaml

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+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: default-http-backend
+  labels:
+    k8s-app: default-http-backend
+  namespace: kube-system
+spec:
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        k8s-app: default-http-backend
+    spec:
+      terminationGracePeriodSeconds: 60
+      containers:
+      - name: default-http-backend
+        # Any image is permissable as long as:
+        # 1. It serves a 404 page at /
+        # 2. It serves 200 on a /healthz endpoint
+        image: gcr.io/google_containers/defaultbackend:1.0
+        livenessProbe:
+          httpGet:
+            path: /healthz
+            port: 8080
+            scheme: HTTP
+          initialDelaySeconds: 30
+          timeoutSeconds: 5
+        ports:
+        - containerPort: 8080
+        resources:
+          limits:
+            cpu: 10m
+            memory: 20Mi
+          requests:
+            cpu: 10m
+            memory: 20Mi
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: default-http-backend
+  namespace: kube-system
+  labels:
+    k8s-app: default-http-backend
+spec:
+  ports:
+  - port: 80
+    targetPort: 8080
+  selector:
+    k8s-app: default-http-backend

examples/customization/configuration-snippets/nginx/ingress.yaml

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+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: nginx-configuration-snippet
+  annotations:
+    kubernetes.io/ingress.class: "nginx"
+    ingress.kubernetes.io/configuration-snippet: |
+      more_set_headers "Request-Id: $request_id";
+
+spec:
+  rules:
+  - host: custom.configuration.com
+    http:
+      paths:
+      - backend:
+          serviceName: http-svc
+          servicePort: 80
+        path: /

examples/customization/configuration-snippets/nginx/nginx-ingress-controller.yaml

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+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: nginx-ingress-controller
+  labels:
+    k8s-app: nginx-ingress-controller
+  namespace: kube-system
+spec:
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        k8s-app: nginx-ingress-controller
+    spec:
+      # hostNetwork makes it possible to use ipv6 and to preserve the source IP correctly regardless of docker configuration
+      # however, it is not a hard dependency of the nginx-ingress-controller itself and it may cause issues if port 10254 already is taken on the host
+      # that said, since hostPort is broken on CNI (https://github.com/kubernetes/kubernetes/issues/31307) we have to use hostNetwork where CNI is used
+      # like with kubeadm
+      # hostNetwork: true
+      terminationGracePeriodSeconds: 60
+      containers:
+      - image: gcr.io/google_containers/nginx-ingress-controller:0.9.0-beta.2
+        name: nginx-ingress-controller
+        readinessProbe:
+          httpGet:
+            path: /healthz
+            port: 10254
+            scheme: HTTP
+        livenessProbe:
+          httpGet:
+            path: /healthz
+            port: 10254
+            scheme: HTTP
+          initialDelaySeconds: 10
+          timeoutSeconds: 1
+        ports:
+        - containerPort: 80
+          hostPort: 80
+        - containerPort: 443
+          hostPort: 443
+        env:
+          - name: POD_NAME
+            valueFrom:
+              fieldRef:
+                fieldPath: metadata.name
+          - name: POD_NAMESPACE
+            valueFrom:
+              fieldRef:
+                fieldPath: metadata.namespace
+        args:
+        - /nginx-ingress-controller
+        - --default-backend-service=$(POD_NAMESPACE)/default-http-backend
+        - --configmap=$(POD_NAMESPACE)/nginx-load-balancer-conf

examples/customization/configuration-snippets/nginx/nginx-load-balancer-conf.yaml

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+apiVersion: v1
+data:
+  proxy-set-headers: "kube-system/custom-headers"
+kind: ConfigMap
+metadata:
+  name: nginx-load-balancer-conf
+  namespace: kube-system