Factoring code to define Article.approved (#15600)

As I'm working on #15359 I wanted to favor using scopes over the raw
`where(approved: true)`.

app/controllers/sidebars_controller.rb

@@ -15,7 +15,7 @@ class SidebarsController < ApplicationController
       .order(hotness_score: :desc)
 
     requires_approval = Campaign.current.articles_require_approval?
-    campaign_articles_scope = campaign_articles_scope.where(approved: true) if requires_approval
+    campaign_articles_scope = campaign_articles_scope.approved if requires_approval
 
     @campaign_articles_count = campaign_articles_scope.count
     @latest_campaign_articles = campaign_articles_scope.limit(5).pluck(:path, :title, :comments_count, :created_at)

app/controllers/stories/tagged_articles_controller.rb

@@ -32,7 +32,7 @@ module Stories
 
     def set_number_of_articles
       @num_published_articles = if @tag_model.requires_approval?
-                                  @tag_model.articles.published.where(approved: true).count
+                                  @tag_model.articles.published.approved.count
                                 elsif Settings::UserExperience.feed_strategy == "basic"
                                   tagged_count
                                 else
@@ -47,7 +47,7 @@ module Stories
     def set_stories
       @stories = Articles::Feeds::Tag.call(@tag, number_of_articles: @number_of_articles, page: @page)
 
-      @stories = @stories.where(approved: true) if @tag_model&.requires_approval
+      @stories = @stories.approved if @tag_model&.requires_approval
 
       @stories = stories_by_timeframe
       @stories = @stories.decorate

app/controllers/stories_controller.rb

@@ -61,7 +61,7 @@ class StoriesController < ApplicationController
       .order(hotness_score: :desc)
 
     requires_approval = Campaign.current.articles_require_approval?
-    campaign_articles_scope = campaign_articles_scope.where(approved: true) if requires_approval
+    campaign_articles_scope = campaign_articles_scope.approved if requires_approval
 
     @campaign_articles_count = campaign_articles_scope.count
     @latest_campaign_articles = campaign_articles_scope.limit(5).pluck(:path, :title, :comments_count, :created_at)

app/models/article.rb

@@ -187,6 +187,11 @@ class Article < ApplicationRecord
   }
   scope :unpublished, -> { where(published: false) }
 
+  # [@jeremyf] For approved articles is there always an assumption of
+  #            published?  Regardless, the scope helps us deal with
+  #            that in the future.
+  scope :approved, -> { where(approved: true) }
+
   scope :admin_published_with, lambda { |tag_name|
     published
       .where(user_id: User.with_role(:super_admin)

app/services/article_api_index_service.rb

@@ -67,7 +67,7 @@ class ArticleApiIndexService
     articles = published_articles_with_users_and_organizations.cached_tagged_with(tag)
 
     articles = if Tag.find_by(name: tag)&.requires_approval
-                 articles.where(approved: true).order(featured_number: :desc)
+                 articles.approved.order(featured_number: :desc)
                elsif top.present?
                  articles.where("published_at > ?", top.to_i.days.ago)
                    .order(public_reactions_count: :desc)