feat: enable incus support in actionsdind container (#10)

- add incus-images backend
- set incus-images as default backend

Reviewed-on: https://git.query.consul/unkin/packer-images/pulls/10

library/locals.pkr.hcl

@@ -7,4 +7,6 @@ locals {
   incus_base_name = "${var.os_name}${var.os_version_major}/${var.os_image}"
   incus_output_image = "${local.incus_base_name}/${var.suffix}"
   is_master  = "${var.git_branch}" == "master"
+  incus_key = vault("kv/data/service/packer/builder/docker-incus-client", "private_key")
+  incus_crt = vault("kv/data/service/packer/builder/docker-incus-client", "public_key")
 }

library/variables.pkr.hcl

@@ -121,3 +121,8 @@ variable "git_branch" {
   type = string
   default = env("GIT_BRANCH")
 }
+
+variable "include_incus_client_certs" {
+  type    = bool
+  default = false
+}