fix: Ticket downloads for multi-attendee orders

[abhinavk96]

Fixes #6091

Short description of what this resolves:

There were several issues at storage and permission level which prevented ticket downloads for multiple attendees.

• There are separate ticket PDFs generated for all ticket holders, and then individual ticket holders.
• These files were overwriting each other, and as such only the last attendee was present in the generated ticket
• Admin, or ticket holders were not being allowed to download tickets due to wrong logical implementation on permission checks

Changes proposed in this pull request:

• Create a new path for combined tickets
• Move away permission control to user model
• Amend permission control to allow admin, and ticket holders to download tickets.

[codecov]

Codecov Report

Merging #6095 into development will decrease coverage by <.01%.
The diff coverage is 14.28%.

@@               Coverage Diff               @@
##           development    #6095      +/-   ##
===============================================
- Coverage        66.17%   66.17%   -0.01%     
===============================================
  Files              285      285              
  Lines            14133    14136       +3     
===============================================
+ Hits              9353     9354       +1     
- Misses            4780     4782       +2

Impacted Files	Coverage Δ
app/api/helpers/order.py	39.06% <ø> (ø)	⬆️
app/api/helpers/storage.py	59.29% <ø> (ø)	⬆️
app/api/auth.py	23.55% <0%> (+0.2%)	⬆️
app/models/user.py	55.55% <20%> (-0.72%)	⬇️

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[iamareebjamal]

What about existing ticket PDFs present in old location?

[abhinavk96]

@iamareebjamal deleted them (manually), the endpoint will recreate them if not found.
*Not deleted on the production server yet

try:
                return return_tickets(file_path, order_identifier)
except FileNotFoundError:
                create_pdf_tickets_for_holder(order)
                return return_tickets(file_path, order_identifier)

This ensures it ^ .