FindCmd::parse currently just creates a FindCmd::Invocation and passes the request's BSON document into it, without actually parsing the request (see here). Instead, parsing is deferred until FindCmd::Invocation::run, where it's one of the first things it does. We should move the parsing logic into FindCmd::parse, since this will allow us to determine if the particular request should be subject to Admission Control or not without an extra request scan.