I need to supply only payload schema for API endpoint without any Pydantic validation (FastAPI==0.110.1, Pydantic v2):

from typing import Literal, Annotated

import uvicorn
from fastapi import FastAPI
from pydantic import BaseModel, Field, RootModel

app = FastAPI()


def get_openapi_extra(model) -> dict:
    return {
        "requestBody": {
            "content": {"application/json": {"schema": model.schema(ref_template="#/components/schemas/{model}")}}
        }
    }


class Cat(BaseModel):
    pet_type: Literal['cat']
    meows: int


class Dog(BaseModel):
    pet_type: Literal['dog']
    barks: float


class Lizard(BaseModel):
    pet_type: Literal['reptile', 'lizard']
    scales: bool


class Model(RootModel):
    root: Annotated[Cat | Dog | Lizard, Field(..., discriminator='pet_type')]


@app.get("/", openapi_extra=get_openapi_extra(Model))
def index():
    return "ok"

In Pydantic v1 and FastAPI==0.98.0 it worked without problems. But when I started to upgrade to Pydantic v2 and FastAPI I faced the next problem:

It seems that FastAPI does not know about Lizard, Dog and Cat schemas…

How to fix it?