roles/mosquitto: Add role to deploy MQTT server

*Mosquitto* implements an MQTT server.  It is the recommended
implementation for using MQTT with Home Assistant.

I have added this role to deploy Mosquitto on the Home Assistant server.
It will be used to send data from custom sensors, such as the
temperature/pressure/humidity sensor connected to the living room wall
display.

roles/mosquitto/tasks/main.yml

@@ -0,0 +1,42 @@
+- name: ensure mosquitto is installed
+  package:
+    name: mosquitto
+    state: present
+  tags:
+  - install
+
+- name: ensure mosquitto certificate is installed
+  copy:
+    src: certs/mosquitto/{{ inventory_hostname }}.cer
+    dest: '{{ mosquitto_certfile }}'
+    mode: '0644'
+  notify:
+  - restart mosquitto
+  when: mosquitto_certfile is defined
+- name: ensure mosquitto private key is installed
+  copy:
+    src: certs/mosquitto/{{ inventory_hostname }}.key
+    dest: '{{ mosquitto_keyfile }}'
+    mode: '0400'
+  notify:
+  - restart mosquitto
+  when: mosquitto_keyfile is defined
+
+- name: ensure mosquitto is configured
+  template:
+    src: mosquitto.conf.j2
+    dest: /etc/mosquitto/mosquitto.conf
+    mode: '0644'
+  notify:
+  - restart mosquitto
+
+- meta: flush_handlers
+
+- name: ensure mosquitto starts at boot
+  service:
+    name: mosquitto
+    enabled: true
+- name: ensure mosquitto is running
+  service:
+    name: mosquitto
+    state: started