Attendees can sign up on the waiting list more than once

Description of the issue 📄

We have a coach who is on the waiting list for our next workshop 10 times. This has happened before where the student was on 3 times.

Screenshots 📷

Steps to fix 🛠

Check in the rsvp method in workshops_controller to see if the user is already waitlisted. I can see there is this code but it doesn't seem to always be working:

      if user_attending_or_waitlisted?(@workshop, current_user)
        return redirect_back fallback_location: root_path, notice: t('workshops.already_wish_to_attend')
      end

It is within an if/else statement so maybe it isn't hitting this part, or the user is clicking on rsvp too quickly before the previous waiting list addition has been complete.

To do 📋

• Claim this issue (comment below, or assign yourself if you are part of the codebar org)
• Fork and clone the repository
• Update the relevant files. Follow the steps to fix section in this issue.
• Commit your changes as one commit. Use the title of this issue as your commit message
• Submit a pull request
• Mention this issue in the PR description by including it's number
• Have your pull request reviewed & merged by a codebar team member

Start in the workshops_controller rsvp method and inspect the user_attending_or_waitlisted? check and its surrounding if/else flow. Reproduce or trace repeated waiting-list submissions, including rapid clicks, then ensure one attendee cannot be added to the same workshop waiting list more than once.