fix get_given_constraint_keys for pydantic 2.1

[jerryjiahaha]

workaround for #169

[mansenfranzen]

Thanks a lot for providing the PR to fix this bug!

We will need a test case to ensure the bug is fixed and won't occur again in the future. Since setting up tests with sphinx/pydantic is not trivial, feel free to allow me to contribute to your PR branch and I'm happy to add the test case.

Apart from that, I'm curious to know how you came up with this solution. Do you have some additional knowledge/docs about how __pydantic_core_schema__["definitions"] behaves? Of course it would be best to open an issue in the pydantic project asking for clarification in the first place but maybe you have some insights here.

[jerryjiahaha]

@mansenfranzen Sorry, I don't know more about __pydantic_core_schema__ design... So I think this PR is temporary modification

__pydantic_core_schema__ may be an internal data structure of pydantic and may not be stable? (Ref: get_pydantic_core_schema doc )

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.29% 🎉

Comparison is base (6d40446) 94.39% compared to head (94e979f) 94.68%.

❗ Current head 94e979f differs from pull request most recent head afe28cb. Consider uploading reports for the commit afe28cb to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #170      +/-   ##
==========================================
+ Coverage   94.39%   94.68%   +0.29%     
==========================================
  Files          12       12              
  Lines        1052     1035      -17     
==========================================
- Hits          993      980      -13     
+ Misses         59       55       -4     

Files Changed	Coverage Δ
...hinxcontrib/autodoc_pydantic/directives/utility.py	96.55% <100.00%> (ø)
sphinxcontrib/autodoc_pydantic/inspection.py	95.34% <100.00%> (+1.38%)	⬆️

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