async fn latest_linking_email_status(
conn: &mut PgConnection,
mail: &CreditRegistrationAccountLinkingEmail,
) -> Result<Option<TeacherLinkingEmailStatus>, ControllerError>async fn latest_linking_email_status(
conn: &mut PgConnection,
mail: &CreditRegistrationAccountLinkingEmail,
) -> Result<Option<TeacherLinkingEmailStatus>, ControllerError>