Use Rails' index_by where it makes sense (#15542)

* Use Rails' index_by where it makes sense

* Fix tests

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/lib/entity_cache.rb

@@ -25,7 +25,7 @@ class EntityCache
     end
 
     unless uncached_ids.empty?
-      uncached = CustomEmoji.where(shortcode: shortcodes, domain: domain, disabled: false).each_with_object({}) { |item, h| h[item.shortcode] = item }
+      uncached = CustomEmoji.where(shortcode: shortcodes, domain: domain, disabled: false).index_by(&:shortcode)
       uncached.each_value { |item| Rails.cache.write(to_key(:emoji, item.shortcode, domain), item, expires_in: MAX_EXPIRATION) }
     end
 

app/lib/settings/scoped_settings.rb

@@ -30,7 +30,7 @@ module Settings
 
     def all_as_records
       vars = thing_scoped
-      records = vars.each_with_object({}) { |r, h| h[r.var] = r }
+      records = vars.index_by(&:var)
 
       Setting.default_settings.each do |key, default_value|
         next if records.key?(key) || default_value.is_a?(Hash)

app/lib/webfinger.rb

@@ -21,7 +21,7 @@ class Webfinger
     private
 
     def links
-      @links ||= @json['links'].map { |link| [link['rel'], link] }.to_h
+      @links ||= @json['links'].index_by { |link| link['rel'] }
     end
   end