Enhancement: Allow defining multiple `ResponseSpec`s for a single status code

[umarbutler]

Summary

Right now it is not possible to define a router to return oneOf multiple different types of data types, you can only use a single data type. This makes it difficult to specify, for example, that a 400 could raise ValidationException or MyCustomValidationException: Type[ValidationException].

Basic Example

{
    400: [
        ResponseSpec(
            data_container=CustomErrorStruct,
            description="Invalid request",
        ),
        ResponseSpec(
            data_container=CustomChildErrorStruct,
            description="Request too long",
        ),
    ]
}

Drawbacks and Impact

No response

Unresolved questions

No response