Add reason param to POST /api/v1/accounts REST API (#12064)

For approval-required registrations mode

spec/services/app_sign_up_service_spec.rb

@@ -38,6 +38,15 @@ RSpec.describe AppSignUpService, type: :service do
       user = User.find_by(id: access_token.resource_owner_id)
       expect(user).to_not be_nil
       expect(user.account).to_not be_nil
+      expect(user.invite_request).to be_nil
+    end
+
+    it 'creates an account with invite request text' do
+      access_token = subject.call(app, good_params.merge(reason: 'Foo bar'))
+      expect(access_token).to_not be_nil
+      user = User.find_by(id: access_token.resource_owner_id)
+      expect(user).to_not be_nil
+      expect(user.invite_request&.text).to eq 'Foo bar'
     end
   end
 end