feat(debian) enable module to work on debian

Add support for Debian based on the documentation in debian wiki
and discussion in [0].

[0]: https://github.com/githubixx/ansible-role-wireguard/issues/5

files/etc/apt/preferences.d/limit-unstable

@@ -0,0 +1,3 @@
+Package: *
+Pin: release a=unstable
+Pin-Priority: 90

tasks/main.yml

@@ -3,6 +3,9 @@
   setup:
 
 - include_tasks: "setup-{{ ansible_os_family|lower }}.yml"
+  when: ansible_os_family.lower() == 'archlinux'
+- include_tasks: "setup-{{ ansible_distribution|lower }}.yml"
+  when: ansible_os_family.lower() != 'archlinux'
 
 - name: Install WireGuard
   package:

tasks/setup-debian.yml

@@ -1,26 +1,28 @@
 ---
-- name: Update APT package cache
-  apt:
-    update_cache: true
-    cache_valid_time: 3600
-  when: ansible_distribution == "Ubuntu"
+- name: Setup WireGuard preference
+  copy:
+    src: etc/apt/preferences.d/limit-unstable
+    dest: /etc/apt/preferences.d/limit-unstable
+    owner: root
+    group: root
+    mode: 0644
   tags:
     - wg-install
 
-- name: Install required packages
-  package:
-    name: "{{ item }}"
+- name: Add WireGuard key
+  apt_key:
+    keyserver: "keyserver.ubuntu.com"
+    id: "8B48AD6246925553"
     state: present
-  with_items:
-    - software-properties-common
-    - linux-headers-{{ ansible_kernel }}
+  run_once: true
   tags:
     - wg-install
 
 - name: Add WireGuard repository
   apt_repository:
-    repo: "ppa:wireguard/wireguard"
+    repo: "deb http://deb.debian.org/debian/ unstable main"
     state: present
     update_cache: yes
+  run_once: true
   tags:
     - wg-install

tasks/setup-ubuntu.yml

@@ -0,0 +1,25 @@
+---
+- name: Update APT package cache
+  apt:
+    update_cache: true
+    cache_valid_time: 3600
+  tags:
+    - wg-install
+
+- name: Install required packages
+  package:
+    name: "{{ item }}"
+    state: present
+  with_items:
+    - software-properties-common
+    - linux-headers-{{ ansible_kernel }}
+  tags:
+    - wg-install
+
+- name: Add WireGuard repository
+  apt_repository:
+    repo: "ppa:wireguard/wireguard"
+    state: present
+    update_cache: yes
+  tags:
+    - wg-install