Rename User.by_authors to with_ids

The "by_authors" scope was the last remaining name from the removed
family of `by_author` scopes. It no longer reflects its purpose: it
simply loads users by IDs.

app/models/community.rb

@@ -49,8 +49,8 @@ class Community < ApplicationRecord
     end
 
     def users_who_topics_author
-      author_ids = topics.pluck(:author_id)
-      User.by_authors(author_ids)
+      ids = topics.pluck(:author_id)
+      User.with_ids(ids)
     end
 
     def author_from_community

app/models/user.rb

@@ -111,7 +111,7 @@ class User < ApplicationRecord
   scope :erased,         -> { where.not(erased_at: nil) }
   scope :active,         -> { excluding(erased) }
   scope :public_for_api, -> { all }
-  scope :by_authors,     ->(author_ids) { where(id: author_ids) }
+  scope :with_ids,       ->(ids) { where(id: ids) }
   scope :by_comments,    ->(commentables) do
     joins(:comments).where("comments.commentable": commentables).distinct
   end