BC: trait Guard check ServiceRequest instead of RequestHead

[RoDmitry]

I was trying to impl Guard for my custom Guard, and I noticed that fn check uses RequestHead, but it could use full ServiceRequest for custom Guard to have access to ServiceRequest.app_data(). Every call of Guard.check() passes ServiceRequest.head() to it (or HttpRequest.head() in the Guard tests).

For example, I'd like to use MySqlPool, that's why I need access to it from ServiceRequest.app_data(). But Guard.check() doesn't allow access to app_data. And I don't see why.

I know that's a breaking change, but now is a perfect timing, because it is beta, right? 😏🤞

[RoDmitry]

Hm.. It's not async also, I didn't see that, sorry. I'm kind of new to the Rust and Actix, so never mind ☺