code: public PactDslRequestWithoutPath headerFromProviderState(String name, String expression, String example) {
      requestGenerators.addGenerator(Category.HEADER, name, new ProviderStateGenerator(expression));
      requestHeaders.put(name, Collections.singletonList(example));
      return this;
    }
docs: Adds a header that will have it's value injected from the provider state
  @param name Header Name
  @param expression Expression to be evaluated from the provider state
  @param example Example value to use in the consumer test