Add instructions for mapping `username` and `userid` claims for LDAP based user stores

[shanggeeth]

Purpose

• Username and User ID claims need to be mapped to the values of Username Attribute and User ID Attribute from user store configuration for a proper authentication flow.
• This PR documents the instructions and the necessity.

Related Issue

• https://github.com/wso2/product-is/issues/20558

[bhagyasakalanka]

@shanggeeth

Can you add a SS or recording on the page view?

[shanggeeth]

Read-write LDAP user store views (7.0 and latest) (Same views for LDAP user stores)

Read-write LDAP user store view (6.0 and 6.1)

Read-write AD user store view (6.0 and 6.1)