Fix Cf-Ray HTTP header not being logged

The Cf-Ray header ends with a suffix of the datacenter (e.g. `-IAD`),
and the regex did not properly handle the dash. This change fixes the
regexp to allow for alphanumeric characters and the dash.

lib/gitlab/logging/cloudflare_helper.rb

@@ -14,7 +14,7 @@ module Gitlab
       def valid_cloudflare_header?(value)
         return false unless value.present?
         return false if value.length > 64
-        return false if value.index(/[^[:alnum:]]/)
+        return false if value.index(/[^[A-Za-z0-9-]]/)
 
         true
       end

spec/lib/gitlab/logging/cloudflare_helper_spec.rb

@@ -19,7 +19,7 @@ describe Gitlab::Logging::CloudflareHelper do
     end
 
     context 'with normal headers' do
-      let(:headers) { { 'Cf-Ray' => SecureRandom.hex, 'Cf-Request-Id' => SecureRandom.hex } }
+      let(:headers) { { 'Cf-Ray' => '592f0aa22b3dea38-IAD', 'Cf-Request-Id' => SecureRandom.hex } }
 
       it 'adds Cf-Ray-Id and Cf-Request-Id' do
         helper.store_cloudflare_headers!(payload, request)