feat: document instance settings

docs/instance.md

@@ -92,6 +92,14 @@ If you click in the **instance settings (gear)** button on the administration in
 
 ![instance_setting](img/instance_setting.png)
 
+You can see that this is the landing page for the datasets settings for the given instance.
+Those settings are sufficiently complex to be detailed apart on [Dataset administration](dataset.md).
+From there, you can add datasets family and also configure other datasets of the existing dataset families.
+When you create a dataset or a family, you have to add a **label** and a **display**.
+The latter figure characterizes the importance of the family or of the dataset in the display order.
+
+In the following, a focus is made on [database configuration](#handle-databases) and on [menu edition](#webpages).
+
 ### Handle databases
 
 This section explain the database configuration for an instance.
@@ -115,10 +123,54 @@ If you click in the **Edit** button, you should land on a self-explanatory form
 
 **Note**: one instance can accept more than one database connection, as hinted by the button **New database**. Hence, accessing datasets not stored in the same database instance.
 
-### Webpage in an instance
+### Menu configuration
+
+To refine the configuration of ANIS instances, ANIS offers the possibility to create so-called:
+
+- **web-pages**: to configure and write landing pages, dataset documentation, core instance content
+- **menus**: to configure a menu on the top navigation bar
+    - contains either **URL** or **web-pages**
+- **URL**: to jump to external URL
+
+Those elements are accessible through the top navigation bar on the [web user interface](web_client.md), always available.
+
+For that, click **Edit menu**.
+
+You should now see a list of elements in the previous listing.
+
+#### Web-pages
+
+Web-pages represents the main way to include specific content in an instance.
+Click **Edit this item (pencil icon)**, you should now see a form on requiring among others, a name, a label, the title and the content.
+
+- The *display* figure in this form represents the priority of appearance on the navigation bar, with higher number appearing first
+- The *title* string is the title appearing for the web-page on the main navigation bar
+- The *content* is pure ***HTML*** that displays on the web-page, it can contains a list of so-called ***dynamic components***
+    - You can stylise the HTML content with the **CSS** associated with it
+
+#### URL
+
+URLs are external links accessible through the main navigation bar.
+
+#### Menus
+
+Menus are top-down listing of **web-pages** and **URLs** accessible from the main navigation bar.
+
 
 ### Instance group
 
+You can protect instances and restrict their access to a set of users.
+
+For that click **Handle instance groups** on the top list of buttons.
+You should now see a list of allowed roles for the selected instance, here the *Default instance*.
+
+You can create and register some roles on this page.
+You then need to add those roles to the running [keycloak](https://www.keycloak.org/) instance, hosted in the `keycloak` container in development mode.
+Attach those roles to registered users with **keycloak**, only registered users under the specified added role have access to the configured instance.
+
+If you've done everything properly, an access restriction to the configured instance is enforced.
+Only properly registered users under the given instance role in the keycloak database can now access this instance.
+
 ## Import and export
 
 Configuring an instance is a lengthy operation.
@@ -143,4 +195,3 @@ Or, you can choose the button **Import an instance**, that offers to select a `j
 ![import_instance](img/import_instance.png)
 
 If no error occurs, the new instance should be available for further configuration.
-