Function map_sqlx_error_with 

pub fn map_sqlx_error_with(
    err: &Error,
    references: &[ForeignKey],
) -> RepositoryError

map_sqlx_error, knowing the entity’s foreign keys: a violation of one of them is RepositoryError::MissingReference with its field. One the list does not name is Unavailable — nothing can tell the caller which input was wrong.