style: formalize preference for if/unless in rubocop (#2816)

.rubocop.yml

@@ -13,3 +13,8 @@ AllCops:
     - 'db/schema*.rb'
     - 'saas/db/migrate/**/*'
     - 'saas/db/saas_schema.rb'
+
+Style/NegatedIf:
+  Enabled: true
+Style/NegatedUnless:
+  Enabled: true

app/models/user/avatar.rb

@@ -39,7 +39,7 @@ module User::Avatar
 
   private
     def avatar_content_type_allowed
-      if !ALLOWED_AVATAR_CONTENT_TYPES.include?(avatar.content_type)
+      unless ALLOWED_AVATAR_CONTENT_TYPES.include?(avatar.content_type)
         errors.add(:avatar, "must be a JPEG, PNG, GIF, or WebP image")
       end
     end

config/puma.rb

@@ -22,7 +22,7 @@ if Fizzy.saas?
   plugin :yabeda_prometheus
 end
 
-if !Rails.env.local?
+unless Rails.env.local?
   # Because we expect fewer I/O waits than Rails apps that connect to the
   # database over the network, let's start with a baseline config of 1
   # worker per CPU, 1 thread per worker and tune it from there.