✨ Add support for instance autocompletion with dataclass_transform (VS Code autocompletion)

[tiangolo]

✨ Add support for dataclass_transform (VS Code autocompletion).

This doesn't change the code at runtime, it doesn't affect how it works. It only implements the spec PEP-0681 which enables editors to provide autocompletion and inline errors (currently VS Code supports it) for models.

It is currently implemented with the early-adopters version described in the draft: https://github.com/microsoft/pyright/blob/main/specs/dataclass_transforms.md#alternate-form

The other option is to require typing-extensions 4.1.0 that includes the accepted spec, but that means changing the requirements, and updating the mypy pre-commit, and updating some type annotations... so the scope of the PR gets extended to other areas...

I'll leave this initial PR as is and then make another one with those changes.

Before:

After:

Note: Check out the alternative implementation, it could supersede this one. It changes more things but in the end it's less lines of code: https://github.com/art049/odmantic/pull/230

[codecov[bot]]

Codecov Report

Merging #229 (07410d4) into master (623fa27) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #229   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           38        38           
  Lines         2725      2730    +5     
  Branches       413       414    +1     
=========================================
+ Hits          2725      2730    +5     

Flag	Coverage Δ
tests-3.6-4-standalone	99.70% <100.00%> (+<0.01%)	:arrow_up:
tests-3.6-4.2-standalone	99.70% <100.00%> (+<0.01%)	:arrow_up:
tests-3.6-4.4-standalone	99.70% <100.00%> (+<0.01%)	:arrow_up:
tests-3.7-4-standalone	99.51% <100.00%> (+<0.01%)	:arrow_up:
tests-3.7-4.2-standalone	99.51% <100.00%> (+<0.01%)	:arrow_up:
tests-3.7-4.4-standalone	99.51% <100.00%> (+<0.01%)	:arrow_up:
tests-3.8-4-replicaSet	97.94% <100.00%> (+<0.01%)	:arrow_up:
tests-3.8-4-standalone	99.45% <100.00%> (+<0.01%)	:arrow_up:
tests-3.8-4.2-sharded	97.94% <100.00%> (+<0.01%)	:arrow_up:
tests-3.8-4.2-standalone	99.45% <100.00%> (+<0.01%)	:arrow_up:
tests-3.8-4.4-standalone	99.45% <100.00%> (+<0.01%)	:arrow_up:
tests-3.9-4-standalone	99.30% <100.00%> (+<0.01%)	:arrow_up:
tests-3.9-4.2-standalone	99.30% <100.00%> (+<0.01%)	:arrow_up:
tests-3.9-4.4-standalone	99.30% <100.00%> (+<0.01%)	:arrow_up:

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Impacted Files	Coverage Δ
odmantic/model.py	100.00% <100.00%> (ø)

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[art049]

Dropped in favor of #230, and since dropping python 3.6 at this point makes sense.