Add custom class to attendees URLs

[enricobattocchi]

Adds a custom class, based on the question name, to URL fields when listing the attendees.
This mimics what happens for other questions where a class tix-<question-name> is added, allowing for further styling. Currently URLs only get the same, generic classes making it very difficult to style them according to their nature.

Fixes WordPress#1379

How to test the changes in this Pull Request:

1. Create a ticket, adding 2 or more URL questions with different names (e.g. "WP.org profile", "Mastodon profile URL", etc.)
2. Register a new attendee, answering to the URL questions above and making sure to answer 'Yes' to 'Do you want to be listed on the public Attendees page? '
3. Visit the Attendees page and check that the URL fields, besides the default tix-field and tix-attendee-url, now have a custom class based on the related question, e.g. tix-wp-org-profile.

[dd32]

I wonder if it would be worth calling it tix-field-{post_name} but other than that, this seems like a safe choice and would've helped me in the past.

[enricobattocchi]

I wonder if it would be worth calling it tix-field-{post_name} but other than that, this seems like a safe choice and would've helped me in the past.

It would make sense, but it would break the pattern of the other questions

[enricobattocchi]

🤦‍♂️ somehow I didn't create the PR on the original repo but in my own fork. Closing this in favor of this other one