Remove Unions

[rosesyrett]

In the last release, Unions were used in some response models, either directly or indirectly, i.e.

@async.get("...", response_model = CoordinateResponse)

CoordinateResponse(BaseModel):
    payload: Union[ .... ]

Or,

@async.get("...", response_model = Union[ArrayResponse, InfoResponse])

Swagger codegen has issues with accurately reproducing java client code that contains oneOf or anyOf, which are generated in the openapi schema by these response models. Therefore, I'm removing them.

[rosesyrett]

Found the following issue for more detail: swagger-api/swagger-codegen#10011

It has been closed but it is unclear to me what the fix is. For now I will just avoid using Unions in models altogether.