EXPOSURE: Support No Return `204` Scenario

[hassanhabib]

Implement the following function:

 ValueTask PostContentAsync<T>(string relativeUrl, T content, string mediaType = "text/json");

This capability will support scenarios where the API doesn't necessarily return anything.
https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-semantics#section-15.3.5