Empty `response_model` gets typehinted to `Any`, which is not imported

[UKnowWhoIm]

How to reproduce:

• Omit the response_model in the router decorator
• Run this on the openapi.json file
• The result's main.py would have used Any for the empty response model and type hint without importing it.

Why does this happen?

My take is that the datamodel-code-generator you use to create schemas and resolve imports won't create this schema as its empty. Therefore its imports won't have Any thus creating an unresolved import.

[UKnowWhoIm]

Is this what you meant by #114?