The output JSON should omit Field when Field.Valid is false

[ggicci]

For example, when encoding the following struct instance to JSON:

type Example struct {
	Name patch.Field[string] `json:"name"`
	Age  patch.Field[int]    `json:"age"`
}

patch := &Example{
	Name: patch.Field[string]{Valid: false},
	Age:  patch.Field[int]{Valid: true, Value: 10},
}

Encode patch to JSON:

Got:

{"name": "", "age": 10}

Expect:

{"age": 10}

[ggicci]

It's not easy to solve this problem currently. Hold.

Keep an eye on the following related issues:

1. proposal: encoding/json: allow skipping field by returning an error in MarshalJSON() ([]byte, error) golang/go#57554
2. https://github.com/go-json-experiment/json
3. proposal: encoding/json, encoding/xml: support zero values of structs with omitempty golang/go#11939