Fix Rubocop offenses (#2296)

* Rerun rubocop --auto-gen-config with --auto-gen-only-exclude --exclude-limit 5000
Move metrics cops in rubocop
Fix Performance/CollectionLiteralInLoop
Fix Performance/MethodObjectAsBlock
Fix RSpec/ClassCheck
Fix RSpec/EmptyExampleGroup
Fix RSpec/IdenticalEqualityAssertion
Fix RSpec/IteratedExpectation
Fix RSpec/LetSetup
Fix Style/MagicCommentFormat
Fix Style/MapToHash
Fix Style/SafeNavigation
Fix Style/SlicingWithRange
Enabled Lint/ConstantDefinitionInBlock
Enabled Lint/EmptyBlock
Enabled RSpec/ContextWording
Enabled RSpec/FilePath
Enabled RSpec/LeakyConstantDeclaration
Enabled RSpec/NamedSubject

* Add CHANGELOG.md

* Add # rubocop:disable RSpec/IteratedExpectation because Rack::Response does not respond to :each_with_index

.rubocop.yml

@@ -12,6 +12,9 @@ require:
 
 inherit_from: .rubocop_todo.yml
 
+Layout/LineLength:
+  Max: 215
+
 Style/Documentation:
   Enabled: false
 
@@ -21,18 +24,34 @@ Style/MultilineIfModifier:
 Style/RaiseArgs:
   Enabled: false
 
-Style/HashEachMethods:
-  Enabled: true
-
-Style/HashTransformKeys:
-  Enabled: true
-
-Style/HashTransformValues:
-  Enabled: true
+Metrics/AbcSize:
+  Max: 45
 
 Metrics/BlockLength:
+  Max: 30
   Exclude:
     - spec/**/*_spec.rb
 
+Metrics/ClassLength:
+  Max: 300
+
+Metrics/CyclomaticComplexity:
+  Max: 15
+
+Metrics/ParameterLists:
+  MaxOptionalParameters: 4
+
+Metrics/MethodLength:
+  Max: 32
+
+Metrics/ModuleLength:
+  Max: 220
+
+Metrics/PerceivedComplexity:
+  Max: 15
+
 RSpec/Capybara/FeatureMethods:
   Enabled: false
+
+RSpec/ExampleLength:
+  Max: 60