feat: Add terraform config for review-app[1]

Also removed the logic for deploying to the long gone aur-dev box.

Ansible will be added in a upcoming commit for configurating and
deploying aurweb on the VM.

[1] https://docs.gitlab.com/ee/ci/review_apps/

ci/tf/main.tf

@@ -0,0 +1,67 @@
+terraform {
+  backend "http" {
+  }
+}
+
+provider "hcloud" {
+  token = var.hcloud_token
+}
+
+provider "dns" {
+  update {
+    server        = var.dns_server
+    key_name      = var.dns_tsig_key
+    key_algorithm = var.dns_tsig_algorithm
+    key_secret    = var.dns_tsig_secret
+  }
+}
+
+resource "tls_private_key" "this" {
+  algorithm = "ED25519"
+}
+
+resource "hcloud_ssh_key" "this" {
+  name       = var.name
+  public_key = tls_private_key.this.public_key_openssh
+}
+
+data "hcloud_image" "this" {
+  with_selector = "custom_image=archlinux"
+  most_recent   = true
+  with_status   = ["available"]
+}
+
+resource "hcloud_server" "this" {
+  name        = var.name
+  image       = data.hcloud_image.this.id
+  server_type = var.server_type
+  datacenter  = var.datacenter
+  ssh_keys    = [hcloud_ssh_key.this.name]
+
+  public_net {
+    ipv4_enabled = true
+    ipv6_enabled = true
+  }
+}
+
+resource "hcloud_rdns" "this" {
+  for_each = { ipv4 : hcloud_server.this.ipv4_address, ipv6 : hcloud_server.this.ipv6_address }
+
+  server_id  = hcloud_server.this.id
+  ip_address = each.value
+  dns_ptr    = "${var.name}.${var.dns_zone}"
+}
+
+resource "dns_a_record_set" "this" {
+  zone      = "${var.dns_zone}."
+  name      = var.name
+  addresses = [hcloud_server.this.ipv4_address]
+  ttl       = 300
+}
+
+resource "dns_aaaa_record_set" "this" {
+  zone      = "${var.dns_zone}."
+  name      = var.name
+  addresses = [hcloud_server.this.ipv6_address]
+  ttl       = 300
+}