docs: add image builder envrionment variable warning

docs/Troubleshooting.md

@@ -67,3 +67,11 @@ If your capi-controller is too new, you can pass a `--core cluster-api:v1.6.1` d
 ## Calico fails in IPVS mode with loadBalancers to expose services
 Calico unfortunately does not test connectivity when it choses a node ip to use for IPVS communication.
 This can be altered manually. More on this topic in [Calicos documentation](https://docs.tigera.io/calico/latest/networking/ipam/ip-autodetection#autodetection-methods).
+
+## Imagebuilder Environment Variables
+[Proxmox VE Image Builder](https://image-builder.sigs.k8s.io/capi/providers/proxmox) and CAPMOX differ in their use of environment variables.
+Trying to use CAPMOX's variables will lead to [image building failure](https://github.com/ionos-cloud/cluster-api-provider-proxmox/issues/52).
+The image builder uses `PROXMOX_USERNAME` as the token name and `PROXMOX_TOKEN` as the token's secret, whereas CAPMOX uses `PROXMOX_TOKEN` as
+the token name and `PROXMOX_SECRET` as the token's secret UUID.
+[Proxmox's API Token Documentation](https://pve.proxmox.com/wiki/Proxmox_VE_API#api_tokens) is closer to CAPMOX's way of implementing authentication,
+therefore this pitfall will likely keep on existing.

docs/Usage.md

@@ -32,6 +32,7 @@ In order to deploy a K8s cluster with CAPMOX, you require the following:
 
   * You can build VM template using [image-builder](https://github.com/kubernetes-sigs/image-builder)
     * **we recommend using** [the Proxmox VE builder](https://image-builder.sigs.k8s.io/capi/providers/proxmox)
+      See our [troubleshooting docs](Troubleshooting.md#imagebuilder_environment_vars) for more information.
     * OR by [Building Raw Images](https://image-builder.sigs.k8s.io/capi/providers/proxmox)
 
 * clusterctl, which you can download it from Cluster API (CAPI) [releases](https://github.com/kubernetes-sigs/cluster-api/releases) on GitHub.