Access request attributes in WebGraphQlInterceptor

[turboezh]

Hi.

I have an issue similar to #626, but I need to access request attributes (ServerRequest.attribute()/ ServletRequest.getAttribute()).

In details:
I need to parse an HTTP-header in a Filter attached to a Spring Security filter chain and create some context from that header. It affects not only /graphql endpoint, so it needs to be done in just one place (in a code) once per request - in a request Filter (I guess this is a right place).
So an idea is to put this context into request attributes, restore it in WebGraphQlInterceptor and re-put into a GraphQLContext. But WebGraphQlRequest does not expose those attributes.