Mypy errors fix

[Domejko]

Description

Regarding #319

• reduced error count from 28 to 7
• In backend/api/invoices/create/services/add.py existing_service default value have been change to 0 because empty string as id was causing ValueError

Edit:

• all errors have been resolved
  
• In pyproject.toml added options for mypy to ignore environment folders. Set incremental option to false due to this error. Disabled note. --explicit_package_bases flag have also now been setup in pyproject.toml so current command to run checks is mypy .

Issue #319 will be closed

Checklist

• Ran the Black Formatter and
  djLint-er on any new code
  (checks
  will
  fail without)
• Made any changes or additions to the documentation where required
• Changes generate no new warnings/errors
• New and existing unit tests pass locally with my
  changes

What type of PR is this?

• 🐛 Bug Fix
• ♻️ Code Refactor

Added/updated tests?

• 🙅 no, because they aren't needed

Related PRs, Issues etc

• Related Issue
• Closes MyPy Error Fix | Open to all #319

[Domejko]

Could you please run test for those changes on your machine, since when I was trying to test this code on mine at the end it just freeze and after a while restart system. Now I'm not sure is it my machine or code because in github actions everything is passing fine with out any issues.

[TreyWW]

Just a bit confused why this should default to 0. POST.get will always return a string. I'm guessing in this case you want 0 to just represent None, but wouldn't it make more sense and be better to just use None? I'm confused how setting it to an integer fixes the errors lol

[Domejko]

oh yes, I just thought of the way to trigger exception and not a ValueError, None probably is a cleaner solution. I will change that since I found also few more issues of this type in that file.
You want me to send them as seperate PR or together with mypy contribution docs update, CI, pre-commit hook ?

[TreyWW]

Separate PR please, thanks. The smaller the PR the quicker I can merge. Otherwise it'll sit there for a month lol

[Domejko]

Hmm now as I have dug deeper into this existing_service = request.POST.get("existing_service", 0) the expected values by existing_service_obj = InvoiceProduct.objects.get(user=request.user, id=existing_service) are of a type str | int so even tho with None it works fine, in terms of type annotations None is a invalid value and 0 or "0" is a valid one. In this case I think that leaving it as 0 will be cleaner than placing # type: ignore since valid product.id never should be a 0.