Skip validation of content-type by TypedBody if body is empty

[kelchm]

Feature Request

In some cases I'd like to be able to make the body of a request optional. This seems to work as expected with @TypedBody, with the exception of it enforcing a check for a Content-Type of application/json:

https://github.com/samchon/nestia/blob/807474a7c7220922822e339f0c7d0dcd6d858491/packages/core/src/decorators/TypedBody.ts#L38-L41

I would argue that specifically in the case of a request with no body, there should be no expectation of a Content-Type header and therefore we should bypass this check. It would then be up to the validator to make a determination of whether this empty body is permissible.

[samchon]

You are meaning that when the request body parameter type is optional, right?