Use serde deserialization instead of constructor for defaults

[PolyProgrammist]

For the following schema:

"field": {
    "allOf": [
        {
            "$ref": "#/components/schemas/MyStruct"
        }
    ],
    "default": "0",
},

The part of generated code is:

...
pub mod defaults {
    pub(super) fn object_field() -> super::MyStruct {
        super::MyStruct("0".to_string())
    }
}
...

It can be, there is no constructor for MyStruct which accepts string.

So it's better to use serde deserialization rather than using constructor

[ahl]

My recollection is that we try to generate a valid constructor. Regardless of how we fix this, typify should not generate code that fails to compile. Can you provide a concise test case?