Passing subdomain: '' to url_for removes the subdomain (instead of ad…
…ding a leading .)
Adding a boolean route constraint checks for presence/absence of request property
Maybe unless options[:subdomain].presence is what we need here? It will be more concise and useful.
That would incorrectly strip the subdomain from the URL when no subdomain option was passed. The current and desirable behaviour is to keep you on your current subdomain.
Add url generation tests for #10185
Add CHANGELOG entries - closes #10180, #10185
Merged in 6183e1a - thanks @derek-watson