Add proxy configuration documentation for CAPX (nutanix-cloud-native#33)

* Add proxy configuration documentation for CAPX

* Update proxy.md

---------

Co-authored-by: Andy Daniel <andy.daniel@nutanix.com>

docs/capx/v1.1.x/experimental/proxy.md

@@ -0,0 +1,62 @@
+# Proxy configuration
+
+!!! warning
+        The scenario and features described on this page are experimental and should not be deployed in production environments.
+
+CAPX can be configured to use a proxy to connect to external networks. This proxy configuration needs to be applied to control plane and worker nodes. 
+
+Follow the steps below to configure a CAPX cluster to use a proxy.
+
+## Steps
+1. Generate a `cluster.yaml` file with the required CAPX cluster configuration. Refer to the [Getting Started](../getting_started.md){target=_blank} page for more information on how to generate a `cluster.yaml` file. Do not apply the `cluster.yaml` file. 
+2. Edit the `cluster.yaml` file and modify the following resources as shown in the [example](#example) below to add the proxy configuration.
+    1. `KubeadmControlPlane`: 
+        * Add the proxy configuration to the `spec.kubeadmConfigSpec.files` list. Do not modify other items in the list.
+        * Add `systemctl` commands to apply the proxy config in `spec.kubeadmConfigSpec.preKubeadmCommands`. Do not modify other items in the list.
+    2. `KubeadmConfigTemplate`: 
+        * Add the proxy configuration to the `spec.template.spec.files` list. Do not modify other items in the list.
+        * Add `systemctl` commands to apply the proxy config in `spec.template.spec.preKubeadmCommands`. Do not modify other items in the list.
+4. Apply the `cluster.yaml` file 
+
+## Example 
+
+```YAML
+---
+# controlplane proxy settings
+kind: KubeadmControlPlane
+spec:
+  kubeadmConfigSpec:
+    files:
+      - content: |
+          [Service]
+          Environment="HTTP_PROXY=<my-http-proxy-configuration>"
+          Environment="HTTPS_PROXY=<my-https-proxy-configuration>"
+          Environment="NO_PROXY=<my-no-proxy-configuration>"
+        owner: root:root
+        path: /etc/systemd/system/containerd.service.d/http-proxy.conf
+      ...
+    preKubeadmCommands:
+      - sudo systemctl daemon-reload
+      - sudo systemctl restart containerd
+      ...
+---
+# worker proxy settings
+kind: KubeadmConfigTemplate
+spec:
+  template:
+    spec:
+      files:
+        - content: |
+            [Service]
+            Environment="HTTP_PROXY=<my-http-proxy-configuration>"
+            Environment="HTTPS_PROXY=<my-https-proxy-configuration>"
+            Environment="NO_PROXY=<my-no-proxy-configuration>"
+          owner: root:root
+          path: /etc/systemd/system/containerd.service.d/http-proxy.conf
+        ...
+      preKubeadmCommands:
+        - sudo systemctl daemon-reload
+        - sudo systemctl restart containerd
+      ...
+```
+

mkdocs.yml

@@ -32,6 +32,7 @@ nav:
               - "Autoscaler": "capx/v1.1.x/experimental/autoscaler.md"
               - "OIDC Integration": "capx/v1.1.x/experimental/oidc.md"
               - "Flow VPC": "capx/v1.1.x/experimental/vpc.md"
+              - "Proxy Configuration": "capx/v1.1.x/experimental/proxy.md"
           - "Troubleshooting": "capx/v1.1.x/troubleshooting.md"
       - "v1.0.x":
           - "Getting Started": "capx/v1.0.x/getting_started.md"