code: @Nonnull
    public Result header(final String name, final Object value) {
      requireNonNull(name, "Header's name is required.");
      requireNonNull(value, "Header's value is required.");
      setHeader(name, value);
      return this;
    }
docs: Sets a response header with the given name and value. If the header had already been set,
  the new value overwrites the previous one.
  
  @param name Header's name.
  @param value Header's value.
  @return This content.