Fix: Workshop capacity checks now properly compare attending count with available spaces

[mroderick]

This PR fixes a bug introduced in #2605 where workshop capacity checks were not working correctly.

Problem

PR #2605 changed the capacity check methods from student_spaces?/coach_spaces? to event_student_spaces?/event_coach_spaces?, but the new methods inherited from EventPresenter called model.student_spaces? which just checks if the attribute is present (truthy), not if spaces are actually available.

This caused workshops to incorrectly show as full when spaces were available, and vice versa.

Solution

Added proper event_student_spaces? and event_coach_spaces? methods to WorkshopPresenter that correctly compare the number of attending students/coaches with the available spaces:

def event_student_spaces?
  model.student_spaces > attending_students.length
end

def event_coach_spaces?
  model.coach_spaces > attending_coaches.length
end

Key Fix

Uses model.student_spaces (the database column) instead of student_spaces (the presenter method that delegates to venue.seats). This ensures that when tests or admins set workshop.student_spaces = 0, the capacity check respects that value rather than reading from the venue.

Testing

• Added spec/presenters/workshop_presenter_capacity_spec.rb with 4 test cases
• All 43 related invitation tests pass
• All 81 presenter tests pass

Bug Report Context

From Slack:

An error has popped up, I'm not sure if it's all workshops or just the latest Barcelona one. But invites have gone out and on the invitation page it says the workshop is full. When I then try to RSVP it adds me to waitilist even though all students spots are still available

I just tried it out on the latest virtual UK workshop and it seemed to work fine. The Berlin one though is broken and doing the same as Barcelona

[KimberleyCook]

Wow!! That was quick 🚀