Write configuration page

docs/reference/configuration.rst

@@ -1,2 +1,63 @@
 Configuration
 =============
+
+Site API has it's own view configuration, available under ``ngcontent_view`` key. Aside from
+:doc:`Query Type </reference/query_types>` options documented separately, this is exactly the same
+as eZ Platform's default view configuration under ``content_view`` key. You can use this
+configuration right after the installation, but note that it won't be used for full views rendered
+for eZ Platform URL aliases right away. Until you configure that, it will be used only when calling
+its controller explicitly with ``ng_content:viewAction``.
+
+To use Site API view rules for pages rendered from eZ Platform URL aliases, you have to enable it
+for a specific siteaccess with the following semantic configuration:
+
+.. code-block:: yaml
+
+    netgen_ez_platform_site_api:
+        system:
+            frontend_group:
+                override_url_alias_view_action: true
+
+Here ``frontend_group`` is the siteaccess group (or a siteaccess) for which you want to activate the
+Site API. This switch is useful if you have some siteaccesses which can't use the it, like custom
+admin or intranet interfaces.
+
+.. note::
+
+  To use Site API view configuration automatically on pages rendered from eZ Platform URL aliases,
+  you need to enable it manually per siteaccess.
+
+One you do this, all your **full view** templates and controllers will need to use Site API to keep
+working. They will be resolved from Site API view configuration, available under ``ngcontent_view``
+key. That means Content and Location variables inside Twig templates will be instances of Site API
+Content and Location value objects, ``$view`` variable passed to your custom controllers will be an
+instance of Site API ContentView variable, and so on.
+
+If needed you can still use ``content_view`` rules. This will allow you to have both Site API
+template override rules as well as original eZ Platform template override rules, so you can rewrite
+your templates bit by bit. You can decide which one to use by calling either
+``ng_content:viewAction`` or ``ez_content:viewAction`` controller.
+
+For example, if using the following configuration:
+
+.. code-block:: yaml
+
+    ezpublish:
+        system:
+            frontend_group:
+                ngcontent_view:
+                    line:
+                        article:
+                            template: "Bundle:content/line:article.html.twig"
+                            match:
+                                Identifier\ContentType: article
+                content_view:
+                    line:
+                        article:
+                            template: "Bundle:content/line:ez_article.html.twig"
+                            match:
+                                Identifier\ContentType: article
+
+Rendering a line view for an article with ``ng_content:viewAction`` would use
+``Bundle:content/line:article.html.twig`` template, while rendering a line view for an article with
+``ez_content:viewAction`` would use ``Bundle:content/line:ez_article.html.twig`` template.

docs/reference/installation_instructions.rst

@@ -21,3 +21,8 @@ Once Site API is installed, activate the bundle in ``app/AppKernel.php`` file by
 
         return $bundles;
     }
+
+And that's it. Once you finish the installation you will be able to use Site API services as you
+would normally do in a Symfony application. However, at this point Site API is not yet fully
+enabled. That is done per siteaccess, see :doc:`Configuration </reference/configuration>` page to
+learn more.