Removes second_user_id and third_user_id From the Articles Table (#10383) [deploy]

* Removes second_user_id and third_user_id from the Articles table

* Adds updated schema file to (fingers crossed) resolve Travis failure

* Adds gaurd clause to data_update script to mitigate db issues

db/migrate/20200918200231_remove_columns_from_articles.rb

@@ -0,0 +1,8 @@
+class RemoveColumnsFromArticles < ActiveRecord::Migration[6.0]
+  def change
+    safety_assured do
+      remove_column :articles, :second_user_id, :bigint
+      remove_column :articles, :third_user_id, :bigint
+    end
+  end
+end

db/schema.rb

@@ -137,12 +137,10 @@ ActiveRecord::Schema.define(version: 2020_10_02_104711) do
     t.integer "score", default: 0
     t.string "search_optimized_description_replacement"
     t.string "search_optimized_title_preamble"
-    t.bigint "second_user_id"
     t.boolean "show_comments", default: true
     t.text "slug"
     t.string "social_image"
     t.integer "spaminess_rating", default: 0
-    t.bigint "third_user_id"
     t.string "title"
     t.datetime "updated_at", null: false
     t.bigint "user_id"

lib/data_update_scripts/20200916202343_backfill_co_author_ids_for_articles.rb

@@ -1,6 +1,9 @@
 module DataUpdateScripts
   class BackfillCoAuthorIdsForArticles
     def run
+      return unless ActiveRecord::Base.connection.column_exists?(:articles, :second_user_id) ||
+        ActiveRecord::Base.connection.column_exists?(:articles, :third_user_id)
+
       articles = Article.where.not(second_user_id: nil).or(Article.where.not(third_user_id: nil))
       articles.find_each do |article|
         co_author_ids = [article.second_user_id, article.third_user_id].compact