Allow timeout to be set when asyncServletModeEnabled=true

[kclaes]

Currently (v7.4.1), the AbstractGraphQLHttpServlet allows you to use an AsyncContext to handle GraphQl queries.

There's a mechanism in place to set the timeout for subscriptions (subscriptionTimeout), but not for the actual query. This results in any query timing out after the default period of 30s (the AsyncContext default expiry).

Can a field be added to the GraphQlConfiguration that sets the timeout for the AsyncContext in AbstractGraphQLHttpServlet.doRequestAsync?

Also, if accepted, this requires the GraphQLWebAutoConfiguration to be adjusted to accomodate this extra parameter in graph-spring-boot-autoconfigure. Let me know if you'd like me to log an issue in that project as well.