models: remove belongs_to_creator macro.

The belongs_to_creator macro was used to initialize the creator_id field
to the CurrentUser. This made tests complicated because it meant you had
to create and set the current user every time you wanted to create an
object, when lead to the current user being set over and over again. It
also meant you had to constantly be aware of what the CurrentUser was in
many different contexts, which was often confusing. Setting creators
explicitly simplifies everything greatly.

app/models/artist.rb

@@ -13,7 +13,7 @@ class Artist < ApplicationRecord
   after_save :clear_url_string_changed
   validate :validate_tag_category
   validates :name, tag_name: true, uniqueness: true
-  belongs_to_creator
+  belongs_to :creator, class_name: "User"
   has_many :members, :class_name => "Artist", :foreign_key => "group_name", :primary_key => "name"
   has_many :urls, :dependent => :destroy, :class_name => "ArtistUrl", :autosave => true
   has_many :versions, -> {order("artist_versions.id ASC")}, :class_name => "ArtistVersion"
@@ -418,15 +418,15 @@ class Artist < ApplicationRecord
       end
     end
 
-    def ban!
+    def ban!(banner: CurrentUser.user)
       Post.transaction do
         CurrentUser.without_safe_mode do
           Post.tag_match(name).each(&:ban!)
 
           # potential race condition but unlikely
           unless TagImplication.where(:antecedent_name => name, :consequent_name => "banned_artist").exists?
-            tag_implication = TagImplication.create!(:antecedent_name => name, :consequent_name => "banned_artist", :skip_secondary_validations => true)
-            tag_implication.approve!(approver: CurrentUser.user)
+            tag_implication = TagImplication.create!(antecedent_name: name, consequent_name: "banned_artist", skip_secondary_validations: true, creator: banner)
+            tag_implication.approve!(approver: banner)
           end
 
           update_column(:is_banned, true)