I have a situation in which I am asking users to enter a site name into a text field with the following rules:
- no spaces
- only lowercase letters, numbers, underscores, and dashes
I would like to validate their input and provide feedback if they don't follow the rules. I believe that the "Field Validation" module for Drupal would provide this service. Just checking to see if there is any option for this in Backdrop CMS core or contrib?