Revert #3377

[martincostello]

Manually revert changes from #3377.

Resolves #3425.

[Copilot]

Pull Request Overview

Revert enum nullability changes introduced in PR #3377, restoring previous behavior for nullable enums in schema generation and tests.

• Tests adjusted to remove nullable enum variants and expect non-nullable schema references.
• Integration test snapshots updated to drop Nullable suffix and schema definitions for nullable enums.
• Core schema generation logic reverted to treat Nullable<T> the same as T, removing special‐case unwrapping and null‐enum handling.

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/Swashbuckle.AspNetCore.SwaggerGen.Test/SchemaGenerator/JsonSerializerSchemaGeneratorTests.cs	Removed InlineData cases for nullable enums
test/Swashbuckle.AspNetCore.Newtonsoft.Test/SchemaGenerator/NewtonsoftSchemaGeneratorTests.cs	Adjusted expected enum counts and reference IDs for nullable enums
test/Swashbuckle.AspNetCore.IntegrationTests/snapshots/*.verified.txt (multiple files)	Replaced *Nullable references with non-nullable schema names and removed nullable enum definitions
src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/SwaggerGenerator.cs	Reverted unwrapping of nullable types when isRequired
src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs	Removed dataProperty nullability unwrapping and null‐enum handling
src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/JsonSerializerDataContractResolver.cs	Restored passing original type rather than unwrapped nullable
src/Swashbuckle.AspNetCore.Newtonsoft/SchemaGenerator/NewtonsoftDataContractResolver.cs	Reverted to resolving contracts on the effective type

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.54%. Comparing base (b28e9c8) to head (c361462).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3436      +/-   ##
==========================================
- Coverage   93.55%   93.54%   -0.02%     
==========================================
  Files         110      110              
  Lines        3834     3825       -9     
  Branches      719      712       -7     
==========================================
- Hits         3587     3578       -9     
  Misses        247      247              

Flag	Coverage Δ
Linux	93.54% <100.00%> (-0.02%)	⬇️
Windows	93.54% <100.00%> (-0.02%)	⬇️
macOS	93.54% <100.00%> (-0.02%)	⬇️

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