Add rubocop-rails

.rubocop.yml

@@ -1,6 +1,8 @@
 inherit_from: .rubocop_todo.yml
 
-require: rubocop-performance
+require:
+  - rubocop-performance
+  - rubocop-rails
 
 AllCops:
   TargetRubyVersion: 2.5

Gemfile

@@ -139,6 +139,7 @@ group :test do
   gem "rails-controller-testing"
   gem "rubocop"
   gem "rubocop-performance"
+  gem "rubocop-rails"
   gem "webmock"
 end
 

Gemfile.lock

@@ -374,6 +374,9 @@ GEM
       unicode-display_width (>= 1.4.0, < 1.7)
     rubocop-performance (1.3.0)
       rubocop (>= 0.68.0)
+    rubocop-rails (2.0.0)
+      rack (>= 2.0)
+      rubocop (>= 0.70.0)
     ruby-openid (2.7.0)
     ruby-progressbar (1.10.1)
     ruby_dep (1.5.0)
@@ -509,6 +512,7 @@ DEPENDENCIES
   rotp
   rubocop
   rubocop-performance
+  rubocop-rails
   sanitize
   sassc-rails
   secure_headers