Add entire auth object to validation context options

We were hoping to get to `auth.strategy` in a payload validation function. It looks like only `isAuthenticated` and `credentials` are passed. Is there a reason `context.auth` can’t be set to `request.auth`? Or could `strategy` and `mode` be added?

https://github.com/hapijs/hapi/blob/master/lib/validation.js#L119
