@spec get_to_and_cc(User.t(), list(String.t()), Activity.t() | nil, String.t()) ::
{list(String.t()), list(String.t())}
def get_to_and_cc(user, mentioned_users, inReplyTo, "public") do
@spec get_to_and_cc(User.t(), list(String.t()), Activity.t() | nil, String.t()) ::
{list(String.t()), list(String.t())}
def get_to_and_cc(user, mentioned_users, inReplyTo, "public") do