Delete `EE::AuditorUser`

- There's no real need to have this module _and_ `EE::User`

- This commit moves the contents of `EE::AuditorUser` to `EE::User`

app/models/ee/auditor_user.rb

-module EE
-  # AuditorUser EE mixin
-  #
-  # This module is intended to encapsulate EE-specific model logic
-  # related to auditor (readonly access to all projects) users. It
-  # is prepended to the `User` model.
-  module AuditorUser
-    extend ActiveSupport::Concern
-    include AuditorUserHelper
-
-    included do
-      # We aren't using the `auditor?` method for the `if` condition here
-      # because `auditor?` returns `false` when the `auditor` column is `true`
-      # and the auditor add-on absent. We want to run this validation
-      # regardless of the add-on's presence, so we need to check the `auditor`
-      # column directly.
-      validate :auditor_requires_license_add_on, if: :auditor
-      validate :cannot_be_admin_and_auditor
-    end
-
-    def cannot_be_admin_and_auditor
-      if admin? && auditor?
-        errors.add(:admin, "user cannot also be an Auditor.")
-      end
-    end
-
-    def auditor_requires_license_add_on
-      unless license_allows_auditor_user?
-        errors.add(:auditor, 'user cannot be created without the "GitLab_Auditor_User" addon')
-      end
-    end
-
-    def auditor?
-      license_allows_auditor_user? && self.auditor
-    end
-
-    def admin_or_auditor?
-      admin? || auditor?
-    end
-  end
-end

app/models/ee/user.rb

@@ -5,6 +5,37 @@ module EE
   # and be prepended in the `User` model
   module User
     extend ActiveSupport::Concern
+    include AuditorUserHelper
+
+    included do
+      # We aren't using the `auditor?` method for the `if` condition here
+      # because `auditor?` returns `false` when the `auditor` column is `true`
+      # and the auditor add-on absent. We want to run this validation
+      # regardless of the add-on's presence, so we need to check the `auditor`
+      # column directly.
+      validate :auditor_requires_license_add_on, if: :auditor
+      validate :cannot_be_admin_and_auditor
+    end
+
+    def cannot_be_admin_and_auditor
+      if admin? && auditor?
+        errors.add(:admin, "user cannot also be an Auditor.")
+      end
+    end
+
+    def auditor_requires_license_add_on
+      unless license_allows_auditor_user?
+        errors.add(:auditor, 'user cannot be created without the "GitLab_Auditor_User" addon')
+      end
+    end
+
+    def auditor?
+      license_allows_auditor_user? && self.auditor
+    end
+
+    def admin_or_auditor?
+      admin? || auditor?
+    end
 
     def access_level
       if admin?

app/models/user.rb

@@ -11,7 +11,6 @@ class User < ActiveRecord::Base
   include TokenAuthenticatable
   prepend EE::GeoAwareAvatar
   prepend EE::User
-  prepend EE::AuditorUser
 
   DEFAULT_NOTIFICATION_LEVEL = :participating