feat: Add option to disable order attachment PDF

[iamareebjamal]

Fixes fossasia/open-event-frontend#4545

[codecov]

Codecov Report

Merging #7139 into development will decrease coverage by 0.01%.
The diff coverage is 20.00%.

@@               Coverage Diff               @@
##           development    #7139      +/-   ##
===============================================
- Coverage        62.79%   62.78%   -0.02%     
===============================================
  Files              262      262              
  Lines            13023    13028       +5     
===============================================
+ Hits              8178     8179       +1     
- Misses            4845     4849       +4     

Impacted Files	Coverage Δ
app/api/helpers/mail.py	27.35% <0.00%> (-1.08%)	⬇️
app/api/helpers/system_mails.py	100.00% <ø> (ø)
config.py	88.46% <100.00%> (+0.14%)	⬆️

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