public Request request() {
    if (!this.resolved) {
      throw new IllegalStateException("template has not been resolved.");
    }
    return Request.create(this.method, this.url(), this.headers(), this.body, this);
  }
Creates a {@link Request} from this template. The template must be resolved before calling this
method, or an {@link IllegalStateException} will be thrown.

@return a new Request instance.
@throws IllegalStateException if this template has not been resolved.
core/src/main/java/feign/RequestTemplate.java