roles/taiga: Deploy Taiga project management app

The *taiga* role installs the three components of Taiga:

* taiga-back
* taiga-events
* taiga-front

*taiga-back* is a Python application. Its dependencies are installed via
`pip` in the *taiga* user's site-packages, and the application itself is
installed by unpacking the archive. *taiga-events* is a Node.js
application. Its dependencies are installed by `npm`, and is itself
installed by unpacking the archive. Finally, *taiga-front* is a
single-page browser application that is installed by unpacking the
archive, and served by Apache.

Taiga requires PostgreSQL and RabbitMQ.

roles/taiga/tasks/postgresql.yml

@@ -0,0 +1,19 @@
+- name: ensure taiga postgresql user exists
+  become: true
+  become_user: postgres
+  postgresql_user:
+    name=taiga
+    state=present
+
+- name: ensure taiga postgresql database exists
+  become: true
+  become_user: postgres
+  postgresql_db:
+    name=taiga
+    owner=taiga
+    encoding=utf-8
+    lc_collate=en_US.UTF-8
+    lc_ctype=en_US.UTF-8
+    state=present
+  notify:
+  - migrate taiga data