When an attempt to add a user fails because the email address is already associated with an existing account in a different role, the system can return a generic processing error rather than a message that identifies the actual cause.

Suggested enhancement: Return a specific, actionable error message when user creation fails due to an email already existing under a different role, distinguishing this case from other request-processing failures.

Benefit: Admins can immediately identify and resolve account conflicts on their own, without needing to contact anyone to interpret a generic failure.