Expose is_auditor user role via API

Similar to how we expose is_admin when
using the user API as an admin,
provide is_auditor field

Changelog: changed

Add changelog entry

changelogs/unreleased/expose-is-auditor.yml

+---
+title: Expose is_auditor user role via API
+merge_request: 61058
+author:
+type: changed

lib/api/entities/user_with_admin.rb

@@ -4,6 +4,7 @@ module API
   module Entities
     class UserWithAdmin < UserPublic
       expose :admin?, as: :is_admin
+      expose :auditor, as: :is_auditor
       expose :note
     end
   end

spec/requests/api/users_spec.rb

@@ -536,6 +536,13 @@ RSpec.describe API::Users do
       expect(json_response.keys).not_to include 'is_admin'
     end
 
+    it "does not return the user's `is_auditor` flag" do
+      get api("/users/#{user.id}", user)
+
+      expect(response).to match_response_schema('public_api/v4/user/basic')
+      expect(json_response.keys).not_to include 'is_auditor'
+    end
+
     it "does not return the user's `highest_role`" do
       get api("/users/#{user.id}", user)
 
@@ -582,6 +589,13 @@ RSpec.describe API::Users do
         expect(json_response['is_admin']).to be(false)
       end
 
+      it 'includes the `is_auditor` field' do
+        get api("/users/#{user.id}", admin)
+
+        expect(response).to match_response_schema('public_api/v4/user/admin')
+        expect(json_response['is_auditor']).to be(false)
+      end
+
       it "includes the `created_at` field for private users" do
         get api("/users/#{private_user.id}", admin)