rubocop: fix various Rubocop warnings.

app/models/artist_version.rb

@@ -32,22 +32,18 @@ class ArtistVersion < ApplicationRecord
   extend SearchMethods
 
   def previous
-    @previous ||= begin
-      ArtistVersion.where("artist_id = ? and created_at < ?", artist_id, created_at).order("created_at desc").limit(1).to_a
-    end
+    @previous ||= ArtistVersion.where("artist_id = ? and created_at < ?", artist_id, created_at).order("created_at desc").limit(1).to_a
     @previous.first
   end
 
   def subsequent
-    @subsequent ||= begin
-      ArtistVersion.where("artist_id = ? and created_at > ?", artist_id, created_at).order("created_at asc").limit(1).to_a
-    end
+    @subsequent ||= ArtistVersion.where("artist_id = ? and created_at > ?", artist_id, created_at).order("created_at asc").limit(1).to_a
     @subsequent.first
   end
 
   def current
     @previous ||= begin
-      ArtistVersion.where("artist_id = ?", artist_id).order("created_at desc").limit(1).to_a
+      ArtistVersion.where(artist_id: artist_id).order("created_at desc").limit(1).to_a
     end
     @previous.first
   end
@@ -66,17 +62,17 @@ class ArtistVersion < ApplicationRecord
   end
 
   def other_names_changed(type)
-    other = self.send(type)
+    other = send(type)
     ((other_names - other.other_names) | (other.other_names - other_names)).length.positive?
   end
 
   def urls_changed(type)
-    other = self.send(type)
+    other = send(type)
     ((urls - other.urls) | (other.urls - urls)).length.positive?
   end
 
   def was_deleted(type)
-    other = self.send(type)
+    other = send(type)
     if type == "previous"
       is_deleted && !other.is_deleted
     else
@@ -85,7 +81,7 @@ class ArtistVersion < ApplicationRecord
   end
 
   def was_undeleted(type)
-    other = self.send(type)
+    other = send(type)
     if type == "previous"
       !is_deleted && other.is_deleted
     else
@@ -94,7 +90,7 @@ class ArtistVersion < ApplicationRecord
   end
 
   def was_banned(type)
-    other = self.send(type)
+    other = send(type)
     if type == "previous"
       is_banned && !other.is_banned
     else
@@ -103,7 +99,7 @@ class ArtistVersion < ApplicationRecord
   end
 
   def was_unbanned(type)
-    other = self.send(type)
+    other = send(type)
     if type == "previous"
       !is_banned && other.is_banned
     else