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/files/taiga-back.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+export PYTHONUNBUFFERED=1
+cd /usr/local/lib/taiga/taiga-back
+exec /usr/local/lib/taiga/venv/bin/gunicorn \
+	--workers 4 \
+	-b [::1]:8001 \
+	taiga.wsgi

roles/taiga/files/taiga-events.service

@@ -0,0 +1,13 @@
+# vim: set ft=systemd :
+[Unit]
+Description=Taiga Events Server
+
+[Service]
+Type=simple
+WorkingDirectory=/usr/local/lib/taiga/taiga-events
+ExecStart=/usr/local/lib/taiga/taiga-events/node_modules/coffeescript/bin/coffee \
+	index.coffee
+User=taiga
+
+[Install]
+WantedBy=multi-user.target

roles/taiga/files/taiga.httpd.conf

@@ -0,0 +1,33 @@
+# vim: set ft=apache :
+ProxyRequests off
+ProxyPreserveHost on
+
+ProxyPass /api http://localhost:8001/api
+ProxyPassReverse /api http://localhost:8001/api
+ProxyPass /admin http://localhost:8001/admin
+ProxyPassReverse /admin http://localhost:8001/admin
+ProxyPass /events ws://localhost:8888/events
+
+Alias /static /usr/local/lib/taiga/taiga-back/static
+<Directory /usr/local/lib/taiga/taiga-back/static>
+	Require all granted
+</Directory>
+
+Alias /media /usr/local/lib/taiga/taiga-back/media
+<Directory /usr/local/lib/taiga/taiga-back/media>
+	Require all granted
+</Directory>
+
+DocumentRoot /usr/local/lib/taiga/taiga-front-dist/dist
+<Directory /usr/local/lib/taiga/taiga-front-dist/dist>
+	Require all granted
+
+	RewriteEngine On
+
+	RewriteCond %{HTTPS} !on
+	RewriteRule /.* https://%{SERVER_NAME}$0
+
+	RewriteCond %{REQUEST_FILENAME} !-d
+	RewriteCond %{REQUEST_FILENAME} !-f
+	RewriteRule ^ index.html [L]
+</Directory>

roles/taiga/files/taiga.service

@@ -0,0 +1,11 @@
+# vim: set ft=systemd :
+[Unit]
+Description=Taiga Backend Server
+
+[Service]
+Type=simple
+User=taiga
+ExecStart=/usr/local/libexec/taiga-back.sh
+
+[Install]
+WantedBy=multi-user.target