$get_contributions(alphabetical_order = TRUE) doesn't reorder authors only

[arnaudgallou]

aut <- Plume$new(tibble::tibble(
  given_name = c("Zip", "Pim"),
  family_name = c("Zap", "Pam"),
  role_1 = c("z", NA),
  role_2 = c("a", "a")
))
aut$get_contributions(roles_first = FALSE, by_author = TRUE, alphabetical_order = FALSE)
#> Z.Z.: z and a
#> P.P.: a
aut$get_contributions(roles_first = FALSE, by_author = TRUE, alphabetical_order = TRUE)
#> Z.Z.: a and z
#> P.P.: a

aut$get_contributions(roles_first = TRUE, by_author = FALSE, alphabetical_order = FALSE)
#> z: Z.Z.
#> a: Z.Z. and P.P.
aut$get_contributions(roles_first = TRUE, by_author = FALSE, alphabetical_order = TRUE)
#> a: P.P. and Z.Z.
#> z: Z.Z.