chore(docs): add documentation for hiding service URLs

Author: SteKoe

spring-boot-admin-docs/src/site/docs/customize/01-customize_ui.md

@@ -75,3 +75,16 @@ spring:
           - name: "journal"
             enabled: false
 ```
+
+## Hide Service URL ==
+
+To hide service URLs in Spring Boot Admin UI entirely, set the following property in your Server's configuration:
+
+| Property name                            | Default | Usage                                                                                                              
+|------------------------------------------|---------|--------------------------------------------------------------------------------------------------------------------
+| `spring.boot.admin.ui.hide-instance-url` | `false` | Set to `true` to hide service URLs as well as actions that require them in UI (e.g. jump to /health or /actuator). 
+
+If you want to hide the URL for specific instances only, you can set the `hide-url` property in the instance metadata
+while registering a service.
+When using Spring Boot Admin Client you can set the property `spring.boot.admin.client.metadata.hide-url=true` in the
+corresponding config file. The value set in `metadata` does not have any effect, when the URLs are disabled in Server.