Convert AuthenticationHelpers module to a patch

This way, we don't need to load ApplicationController in a
config.to_prepare block either.

Author: mamhoff

.rubocop_todo.yml

@@ -21,7 +21,6 @@ Gemspec/OrderedDependencies:
 Layout/ArgumentAlignment:
   Exclude:
     - 'app/models/spree/user.rb'
-    - 'lib/spree/authentication_helpers.rb'
     - 'spec/controllers/spree/user_sessions_controller_spec.rb'
     - 'spec/features/sign_out_spec.rb'
 
@@ -351,7 +350,6 @@ Style/GuardClause:
     - 'db/migrate/20120203010234_add_reset_password_sent_at_to_spree_users.rb'
     - 'db/migrate/20190125170630_add_reset_password_token_index_to_spree_users.rb'
     - 'db/migrate/20200417153503_add_unconfirmed_email_to_spree_users.rb'
-    - 'lib/spree/authentication_helpers.rb'
 
 # Offense count: 1
 # This cop supports safe autocorrection (--autocorrect).

app/patches/controllers/solidus_auth_devise/application_controller_patch.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module SolidusAuthDevise
+  module ApplicationControllerPatch
+    def self.prepended(base)
+      return unless base.respond_to?(:helper_method)
+
+      base.send(:helper_method, :spree_current_user)
+
+      return unless SolidusSupport.frontend_available?
+
+      base.send(:helper_method, :spree_login_path)
+      base.send(:helper_method, :spree_signup_path)
+      base.send(:helper_method, :spree_logout_path)
+    end
+
+    def spree_current_user
+      current_spree_user
+    end
+
+    if SolidusSupport.frontend_available?
+      delegate :login_path, :signup_path, :logout_path,
+        to: :spree,
+        prefix: :spree
+    end
+
+    ApplicationController.prepend self
+  end
+end

lib/solidus_auth_devise.rb

@@ -10,5 +10,3 @@
 require 'solidus_auth_devise/configuration'
 require 'solidus_auth_devise/version'
 require 'solidus_auth_devise/engine'
-
-require 'spree/authentication_helpers'

lib/spree/auth/engine.rb

@@ -24,8 +24,6 @@ class Engine < Rails::Engine
       config.to_prepare do
         Spree::Auth::Engine.prepare_backend if SolidusSupport.backend_available?
         Spree::Auth::Engine.prepare_frontend if SolidusSupport.frontend_available?
-
-        ApplicationController.include Spree::AuthenticationHelpers
       end
 
       def self.redirect_back_on_unauthorized?