Create a new {@code WebTarget} instance by appending path to the URI ofthe current target instance.
When constructing the final path, a '/' separator will be inserted between the existing path and the supplied path if necessary. Existing '/' characters are preserved thus a single value can represent multiple URI path segments.
A snapshot of the present configuration of the current (parent) target instance is taken and is inherited by the newly constructed (child) target instance.
@param path the path, may contain URI template parameters.
@return a new target instance.
@throws NullPointerException if path is {@code null}.