Merging this PR will not alter performance

✅ 20 untouched benchmarks

_{Comparing ilovemesomeramen:master (7e1da42) with master (bc9ad6b)¹}

@ilovemesomeramen, thank you for your interest and efforts!
Can you come up with a more realistic code example? Ideally something that we can not do in a simpler way

@YuriiMotov What do you mean exactly?

The provided example is exactly the issue which this PR solved, this example worked in 0.124.0 but does not in 0.124.1

A little bit of context why this is needed:
I often design my APIs in such a way that it easy to extend the models in the future.
So if i know a specific model will be discriminated in the future i want the OpenAPI spec to reflect that immediately.

the provided test case is based on this test: tests/test_arbitrary_types.py

The Problem is the Union with a single value in it this worked before and no longer works since the type is not properly extracted.