Strip trailing whitespace from validation response

Strips trailing whitespace before checking site validation.

ee/app/services/dast_site_validations/validate_service.rb

@@ -41,7 +41,7 @@ module DastSiteValidations
 
       case dast_site_validation.validation_strategy
       when 'text_file'
-        response.content_type == 'text/plain' && response.body == token
+        response.content_type == 'text/plain' && response.body.rstrip == token
       when 'header'
         response.headers[DastSiteValidation::HEADER] == token
       else

ee/changelogs/unreleased/philipcunningham-strip-newlines-from-http-response-in-dast-site-valida.yml

+---
+title: Strip trailing whitespace from DAST site validation HTTP response body
+merge_request: 53951
+author:
+type: changed

ee/spec/services/dast_site_validations/validate_service_spec.rb

@@ -129,6 +129,14 @@ RSpec.describe DastSiteValidations::ValidateService do
 
         it_behaves_like 'a validation'
 
+        context 'when the http response body has trailing newlines after the token' do
+          let(:token) { dast_site_validation.dast_site_token.token + "\n\n" }
+
+          it 'does not raise an exception' do
+            expect { subject }.not_to raise_error(DastSiteValidations::ValidateService::TokenNotFound)
+          end
+        end
+
         context 'when content type is incorrect' do
           let(:headers) { { 'Content-Type' => 'text/html; charset=UTF-8' } }