how about adding extractor： ValidatedJson<T>

[zishon]

how about adding extractor： ValidatedJson
which T derive validator::Validate
and the behavior should be

1. if the header does not have Content-Type: application/json，then content-type error
2. if the request body can't be deserialized，then not a valid json string error
3. if the payload ( deserialized into T) validate fails （payload.validate()）, then validate error
4. if no error happens, then go ahead.

[mladedav]

Do you mean having something like axum-garde inside axum-extra?

[zishon]

Yes, sort of.