pub async fn fetch_user_mailchimp_id_mapping(
conn: &mut PgConnection,
course_language_group_id: Uuid,
user_ids: &[Uuid],
) -> Result<HashMap<Uuid, String>>Expand description
Fetches user_id -> user_mailchimp_id for the given course language group and user IDs (e.g. after syncing to Mailchimp). Only includes entries with a non-null user_mailchimp_id.