Predetermine authentication methods

Author: MarcialRosales

docs/management/index.md

@@ -658,6 +658,41 @@ And this is the management UI with Basic Authentication activated (`management.o
 
 ![More than one OAuth 2.0 resource, with oauth_disable_basic_auth = false](./management-oauth-many-with-basic-auth.png)
 
+### Preselect or predetermine authentication mechanism {#preselect-auth-mechanism}
+
+By default, when users navigate to the management UI home page, they see all available authentication mechanisms and can choose which one to use.
+However, in some scenarios, users may be routed to the management UI with an authentication mechanism already preselected or predefined. This allows external systems to guide users to a specific authentication flow.
+
+To preselect or predetermine the authentication mechanism, users must sent to the `/login` endpoint with the 
+appropriate request parameters. And the management ui redirects them back to the home page configured according
+to their preferred authentication mechanism. 
+
+The following request parameters control the behaviour:
+
+#### Preselection Mode (preferred_auth_mechanism)
+
+Use the `preferred_auth_mechanism` parameter to preselect an authentication method while still showing all options.
+
+- **OAuth 2.0 resource**: `preferred_auth_mechanism=oauth2:rabbit_dev`
+  - Preselects the OAuth 2.0 resource server, e.g.  `rabbit_dev`
+  - Expands the OAuth 2.0 section and collapses the basic authentication section in the home page
+
+- **Basic authentication**: `preferred_auth_mechanism=basic`
+  - Preselects basic authentication
+  - Expands the basic authentication section and collapses the OAuth 2.0 section
+  
+#### Strict Mode (strict_auth_mechanism)
+
+Use the `strict_auth_mechanism parameter` to show only the specified authentication method. Other methods are hidden.
+
+- **OAuth 2.0 resource only**: `/login?strict_auth_mechanism=oauth2:rabbit_dev`
+  - Shows only the "Click here to login" button for the `rabbit_dev` resource server
+  - No other authentication options are displayed
+
+- **Basic authentication only**: `/login?strict_auth_mechanism=basic`
+  - Shows only the basic authentication form
+  - No OAuth 2.0 options are displayed
+
 ### Troubleshooting {#troubleshooting}
 
 [Troubleshooting management UI access in OAuth 2-enabled clusters](./troubleshooting-oauth2#management-ui) is a companion guide