Added a new doc page about instance configuration

docs/configuration.rst

+Instance configuration
+======================
+
+General configuration is achieved using two type of settings.
+
+Environment variables
+---------------------
+
+Those are located in your ``.env`` file, which you should have created
+during installation.
+
+Options from this file are heavily commented, and usually target lower level
+and technical aspects of your instance, such as database credentials.
+
+.. note::
+
+    You should restart all funwhale processes when you change the values
+    on environment variables.
+
+
+Instance settings
+-----------------
+
+Those settings are stored in database and do not require a restart of your
+instance after modification. They typically relate to higher level configuration,
+such your instance description, signup policy and so on.
+
+There is no polished interface for those settings, yet, but you can view update
+them using the administration interface provided by Django (the framework funkwhale is built on).
+
+The URL should be ``/api/admin/dynamic_preferences/globalpreferencemodel/`` (prepend your domain in front of it, of course).
+
+If you plan to use acoustid and external imports
+(e.g. with the youtube backends), you should edit the corresponding
+settings in this interface.

docs/index.rst

@@ -13,6 +13,7 @@ Funkwhale is a self-hosted, modern free and open-source music server, heavily in
 
    features
    installation/index
+   configuration
    importing-music
    changelog