Add tutorial: Ephemeral Kubernetes clusters on Hetzner with kobe

[0xPxt]

This tutorial provisions one small Hetzner Cloud server, runs the open-source kobe operator on it, and from then on leases warm, disposable k3s clusters from a pool.

I have read and understood the Contributor's Certificate of Origin available at the end of
https://raw.githubusercontent.com/hetzneronline/community-content/master/tutorial-template.md and I hereby certify that I meet the contribution criteria described in it.
Signed-off-by: Aleix Raventos aleix.raventos@zondax.ch

[svenja11]

Thank you for your contribution @0xPxt!

In step 2, I ran into an error:

holu@example:~/kobe/demo/hetzner$ ./demo tf up

[...]

Plan: 4 to add, 0 to change, 0 to destroy.

Changes to Outputs:
  + join_token      = (known after apply)
  + kubeconfig_path = "/home/holu/.kube/hetzner-kobe-demo-config"
╷
│ Error: 2001:db8:5678::1/32 is not the start of the cidr block 2001:db8::/32
│
│   with hcloud_firewall.demo,
│   on main.tf line 61, in resource "hcloud_firewall" "demo":
│   61: resource "hcloud_firewall" "demo" {
│
╵
╷
│ Error: 2001:db8:5678::1/32 is not the start of the cidr block 2001:db8::/32
│
│   with hcloud_firewall.demo,
│   on main.tf line 61, in resource "hcloud_firewall" "demo":
│   61: resource "hcloud_firewall" "demo" {
│
╵
╷
│ Error: 2001:db8:5678::1/32 is not the start of the cidr block 2001:db8::/32
│
│   with hcloud_firewall.demo,
│   on main.tf line 61, in resource "hcloud_firewall" "demo":
│   61: resource "hcloud_firewall" "demo" {
│
╵

==> Outputs
$ /usr/bin/terraform -chdir=/home/holu/kobe/demo/hetzner/terraform output
╷
│ Warning: No outputs found
│
│ The state file either has no outputs defined, or all the defined outputs are empty. Please define an output in your
│ configuration with the `output` keyword and run `terraform refresh` for it to become available. If you are using
│ interpolation, please verify the interpolated value is not empty. You can use the `terraform console` command to
│ assist.
╵
Done. Next:
  export HCLOUD_TOKEN=...                         # already set
  ./demo up                                       # helm install
  ./demo tunnel                                   # terminal B

It looks like https://icanhazip.com returned the IPv6 and caused an error. On my local device, I replaced this line in kobe/demo/hetzner/terraform/main.tf for a quick fix:

# Old line
  api_cidr = var.allowed_api_cidr != "" ? var.allowed_api_cidr : "${data.external.my_ip[0].result.ip}/32"

# New line
  api_cidr = var.allowed_api_cidr != "" ? var.allowed_api_cidr : "203.0.113.1/32"

Can you please update main.tf in the repository so that it grabs the IPv4 address automatically?

FYI You can check your IP at https://ip.hetzner.com/ as well:

curl -4 https://ip.hetzner.com