Fix proffered username sso configuration (#243)

* Adding the initial updates to the documentation for release 2.8.0

Signed-off-by: Aindriu Lavelle <aindriu.lavelle@aiven.io>

* Improve SSO setup documentation

Signed-off-by: Aindriu Lavelle <aindriu.lavelle@aiven.io>

* Update the klaw spelling for the attribute name

Signed-off-by: Aindriu Lavelle <aindriu.lavelle@aiven.io>

* fix sentences

* Only need this documenation for third party providers

Signed-off-by: Aindriu Lavelle <aindriu.lavelle@aiven.io>

* Update docs/authentication-authorization/authentication/third-party-account.md

Co-authored-by: Murali Basani <muralidhar.basani@aiven.io>

---------

Signed-off-by: Aindriu Lavelle <aindriu.lavelle@aiven.io>
Co-authored-by: Harshini Rangaswamy <harshini.rangaswamy@aiven.io>
Co-authored-by: Murali Basani <muralidhar.basani@aiven.io>
Co-authored-by: Mirjam Aulbach <mirjam.aulbach@aiven.io>

.github/vale/styles/Klaw/spelling-klaw-vocabulary.txt

@@ -79,4 +79,5 @@ gtag
 UI
 unencrypted
 kwregisterusers
-Json
+Json
+preferred_username

docs/authentication-authorization/authentication/third-party-account.md

@@ -46,7 +46,13 @@ module.
    The `imageURI` property specifies the URL of the logo image. The image must be uploaded to
    the `assets/images/clients` folder before you can use this property.
 
-7. If you have already signed up, you will be directed to the Klaw home
+7. Each SSO provider can have a different "preferred username" attribute that identifies your user correctly.
+   Check your provider's documentation and select the attribute/claim that defines the username/login name.
+   Update this attribute in the `application.properties` file, replacing 'preferred_username' with their attribute.
+
+   `klaw.ad.username.attribute=preferred_username`
+
+8. If you have already signed up, you will be directed to the Klaw home
    page.
 
    ![image](../../../static/images/authentication/OAuthLogin.png)
@@ -57,7 +63,7 @@ module.
    Login page for third-party account is not fully updated.
    :::
 
-8. If this is your first time logging in, you will be presented with a
+9. If this is your first time logging in, you will be presented with a
    signup form to fill in. On submission, a request will be created for
    the Klaw Administrator to approve or decline.