VEN-1539 Exclude internal organisations from tax

[kristianjokela]

Description ✨

Currently all prices are set with tax, and tax is calculated seperately as totalPretaxPrice and totalTaxPercentage from the original price. However, internal customers should receive their invoices without tax (as per ticket van-1539). This adds a case to price calculation that returns a pretax value for the price for internal customers.

Issues 🐛

https://helsinkisolutionoffice.atlassian.net/browse/VEN-1539

Closes 🙅‍♀️

VEN-1539:

Related 🤝

Testing ⚗️

Automated tests ⚙️️

Manual testing 👷‍♂️

Screenshots 📸

Additional notes 🗒️

[codecov-commenter]

Codecov Report

Merging #701 (005d2bd) into master (5cc61c7) will decrease coverage by 0.01%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##           master     #701      +/-   ##
==========================================
- Coverage   85.93%   85.91%   -0.02%     
==========================================
  Files         150      150              
  Lines        9048     9050       +2     
  Branches     1455     1456       +1     
==========================================
  Hits         7775     7775              
- Misses       1084     1085       +1     
- Partials      189      190       +1     

Impacted Files	Coverage Δ
payments/utils.py	83.61% <50.00%> (-0.47%)	⬇️
payments/models.py	89.56% <100.00%> (ø)

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