[12.0] [IMP] shopinvader: Allows to download paid invoices for confirmed sale order

[lmignon]

foward port of #366

[codecov-io]

Codecov Report

Merging #483 into 12.0 will decrease coverage by 0.01%.
The diff coverage is 83.95%.

@@            Coverage Diff             @@
##             12.0     #483      +/-   ##
==========================================
- Coverage   91.26%   91.25%   -0.02%     
==========================================
  Files         104      105       +1     
  Lines        2898     2973      +75     
==========================================
+ Hits         2645     2713      +68     
- Misses        253      260       +7

Impacted Files	Coverage Δ
shopinvader/services/abstract_mail.py	88.63% <ø> (-1.16%)	⬇️
shopinvader/services/service.py	77.5% <100%> (+1.5%)	⬆️
shopinvader/services/sale.py	97.61% <100%> (+0.84%)	⬆️
shopinvader/controllers/main.py	92.3% <60%> (-4.84%)	⬇️
shopinvader/services/invoice.py	81.66% <81.66%> (ø)
shopinvader/models/account_invoice.py	100% <0%> (+54.54%)	⬆️

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[lmignon]

/ocabot merge minor

[shopinvader-git-bot]

Hey, thanks for contributing! Proceeding to merge this for you.
Prepared branch 12.0-ocabot-merge-pr-483-by-lmignon-bump-minor, awaiting test results.

[shopinvader-git-bot]

Congratulations, your PR was merged at 401aa1e. Thanks a lot for contributing to shopinvader. ❤️