Update docs.

docs/sections/installation.rst

@@ -46,5 +46,4 @@ Generate server RSA key and run migrations (if you don't)::
 
 Add required variables to your project settings::
 
-    SITE_URL = 'http://localhost:8000'
     LOGIN_URL = '/accounts/login/'

docs/sections/settings.rst

@@ -5,13 +5,6 @@ Settings
 
 Customize your provider so fit your project needs.
 
-SITE_URL
-========
-
-REQUIRED. ``str``. The OP server url.
-
-For example ``http://localhost:8000``.
-
 LOGIN_URL
 =========
 
@@ -19,6 +12,15 @@ REQUIRED. ``str``. Used to log the user in. `Read more in Django docs <https://d
 
 ``str``. Default is ``/accounts/login/``.
 
+SITE_URL
+========
+
+OPTIONAL. ``str``. The OP server url.
+
+If not specified will be automatically generated using ``request.scheme`` and ``request.get_host()``.
+
+For example ``http://localhost:8000``.
+
 OIDC_AFTER_USERLOGIN_HOOK
 =========================