I would like to allow only one contact to sign up for a specific role in an event, using the Drupal 7 webform. The role is 'Team Lead' and obviously there should only be one of those! The other role that's allowed is for 'Team Member'. There is a single maximum number for an event, of course but it's not 'by role'. Is there a way to restrict the number of contacts for a given role using webform - or even either of the other form builders in Civi (Form Builder or Form Processor)?
Drupal's Webform has a 'validation' component that can do things like this - e.g. as soon as a submission has been received with a specific value in that form element, it can be configured to prevent future submissions with the same value (i.e. 'uniqueness'). You'd need to create the form in a way that can use this kind of validation, e.g. a checkbox that says "Team Lead", as opposed to being one of a selection of roles, some of which allow multiples.