Add config flow and device registry to fritzbox integration

source/_integrations/fritzbox.markdown

@@ -30,31 +30,38 @@ There is currently support for the following device types within Home Assistant:
 - [FRITZ!DECT 301](https://en.avm.de/products/fritzdect/fritzdect-301/)
 - [Eurotronic Comet DECT](https://eurotronic.org/produkte/elektronische-heizkoerperthermostate/sparmatic-comet/)
 
-## Setup
+## Configuration
+
+To add the AVM FRITZ!Box integration to your installation, go to **Configuration** -> **Integrations** in the UI, click the button with `+` sign and from the list of integrations select **AVM FRITZ!Box**.
+
+If you have enabled SSDP discovery, it’s likely that you just have to confirm the detected device with username and password.
+
+### Configuration via YAML
+
+YAML configuration is still around for people that prefer YAML, but it's deprecated and you should not use it anymore.
 
 ```yaml
 # Example configuration.yaml entry
 fritzbox:
   devices:
-    - host: fritz.box
-      username: YOUR_USERNAME
-      password: YOUR_PASSWORD
+    - password: YOUR_PASSWORD
 ```
 
 {% configuration %}
 devices:
   description: A list of FRITZ!Box devices.
-  required: true
   type: map
   keys:
     host:
       description: The hostname or IP address of the FRITZ!Box.
-      required: true
+      required: false
       type: string
+      default: fritz.box
     username:
       description: The username for Smart Home access.
-      required: true
+      required: false
       type: string
+      default: admin
     password:
       description: The password of the user.
       required: true