added support and tests for pydantic dataclasses

[dconathan]

Fixes #265

Summary of changes:

• in fastapi.utils.create_cloned_field we coerce a pydantic dataclass to its BaseModel version using the __pydantic_model__ attribute
• changed the test_serialize_response.py test to actually test serializing the response and created a separate test test_validate_response.py which tests for appropriate ValidationErrors
• created *_dataclass.py variants of test_serialize_response and test_validate_resonse

[codecov]

Codecov Report

Merging #454 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #454    +/-   ##
======================================
  Coverage     100%   100%            
======================================
  Files         240    251    +11     
  Lines        5626   5868   +242     
======================================
+ Hits         5626   5868   +242

Impacted Files	Coverage Δ
tests/test_serialize_response.py	100% <100%> (ø)	⬆️
tests/test_validate_response.py	100% <100%> (ø)
tests/test_validate_response_dataclass.py	100% <100%> (ø)
tests/test_serialize_response_dataclass.py	100% <100%> (ø)
fastapi/utils.py	100% <100%> (ø)	⬆️
tests/test_additional_responses_router.py	100% <0%> (ø)	⬆️
fastapi/dependencies/utils.py	100% <0%> (ø)	⬆️
fastapi/openapi/utils.py	100% <0%> (ø)	⬆️
fastapi/routing.py	100% <0%> (ø)	⬆️
fastapi/openapi/models.py	100% <0%> (ø)	⬆️
... and 11 more

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[tiangolo]

Great! Thanks a lot! 🚀 🍰

[manojlds]

Is this available for use?

[zamiramir]

Is this available for use?

Released with 0.37.0

• Add support and tests for Pydantic dataclasses in response_model. PR added support and tests for pydantic dataclasses #454 by @dconathan.