Fix #75: changelog

changes/changelog.d/75.feature

+Subsonic API implementation to offer compatibility with existing clients such as DSub (#75)
+
+Subsonic API
+^^^^^^^^^^^^
+
+This release implements some core parts of the Subsonic API, which is widely
+deployed in various projects and supported by numerous clients.
+
+By offering this API in Funkwhale, we make it possible to access the instance
+library and listen to the music without from existing Subsonic clients, and
+without developping our own alternative clients for each and every platform.
+
+Most advanced Subsonic clients support offline caching of music files,
+playlist management and search, which makes them well-suited for nomadic use.
+
+Please head over :doc:`users/apps` for more informations about supported clients
+and user instructions.
+
+At the instance-level, the Subsonic API is enabled by default, but require
+and additional endpoint to be added in you reverse-proxy configuration.
+
+On nginx, add the following block::
+
+    location /rest/ {
+        include /etc/nginx/funkwhale_proxy.conf;
+        proxy_pass   http://funkwhale-api/api/subsonic/rest/;
+    }
+
+On Apache, add the following block::
+
+    <Location "/rest">
+        ProxyPass ${funkwhale-api}/api/subsonic/rest
+        ProxyPassReverse ${funkwhale-api}/api/subsonic/rest
+    </Location>
+
+The Subsonic can be disabled at the instance level from the django admin.
+
+.. note::
+
+    Because of Subsonic's API design which assumes cleartext storing of
+    user passwords, we chose to have a dedicated, separate password
+    for that purpose. Users can generate this password from their
+    settings page in the web client.