roles/hassdb: Deploy Home Assistant database

Normally, Home Assistant uses a SQLite database for storing state
history.  On a Raspberry Pi with only an SD card for storage like
*hass1.pyrocufflink.blue*, this can become extremely slow, especially
for large data sets.  To speed up features like history and logbook,
Home Assistant supports using an external database engine such as
PostgreSQL or MariaDB.

The *hassdb* role and corresponding `hassdb.yml` playbook deploys a
PostgreSQL server for Home Assistant to use.  It needs only to create
the role and database, as Home Assistant manages its own schema.

roles/hassdb/tasks/main.yml

@@ -0,0 +1,21 @@
+- name: ensure psycopg2 is installed
+  package:
+    name: python-psycopg2
+    state: present
+  tags: install
+
+- name: ensure homeassistant postgresql user exists
+  become: true
+  become_user: postgres
+  postgresql_user:
+    name: homeassistant
+    password: '{{ hassdb_password }}'
+  tags: pg-user
+
+- name: ensure homeassistant postgresql database exists
+  become: true
+  become_user: postgres
+  postgresql_db:
+    name: homeassistant
+    owner: homeassistant
+  tags: pg-db