Cast dict as model type if annotated

[masenf]

Describe the bug
Event handlers always seem to get a dict even when the user expects to get a particular type.

To Reproduce

import reflex as rx


class Amigo(rx.Base):
    nombre: str
    anos: int

class State(rx.State):
    amigos: list[Amigo] = [
        Amigo(nombre="Juan", anos=20),
        Amigo(nombre="Pedro", anos=30),
        Amigo(nombre="Maria", anos=40),
        Amigo(nombre="Jose", anos=50),
    ]

    amigo_actual: Amigo | None

    def set_amigo_actual(self, amigo: Amigo) -> None:
        print(repr(amigo))
        self.amigo_actual = amigo


def hacer_amigo(a: Amigo) -> rx.Component:
    return rx.button(a.nombre, on_click=State.set_amigo_actual(a))


def index() -> rx.Component:
    return rx.container(
        rx.color_mode.button(position="top-right"),
        rx.vstack(
            rx.heading("Welcome to Reflex!", size="9"),
            rx.text(f"Amigo Actual: {State.amigo_actual.nombre}"),
            rx.foreach(
                State.amigos,
                hacer_amigo,
            )
        ),
        rx.logo(),
    )


app = rx.App()
app.add_page(index)

Expected behavior
The argument received by the set_amigo_actual event handler should be an Amigo, not a dict.

Specifics (please complete the following information):

• Python Version: 3.12
• Reflex Version: 0.6.4a3
• OS: macOS / Any

Additional context
From this forum thread https://forum.reflex.dev/t/understanding-state-types/488

However this is a long-standing problem in Reflex in that arguments passed to event handlers are always the bare un-JSON'd type, rather than the preferred model type.

There is some provision for casting number-type arguments to actual int/float before passing them through to the event handler, but this logic does not apply for dict types that are annotated with another, specific type.

[linear]

ENG-4023 Cast dict as model type if annotated

[benedikt-bartscher]

I think we need a flexible way to register deserialization/unmarshalling functions like reflex already does for serialization