🍓SwifQLable: Implement convenient execute method

When you have only one complex query in route handler and it shouldn't be wrapped into transaction you could use this convenient method which will establish database connection by itself

func someComplexQueryHandler(_ req: Request) throws -> EventLoopFuture<[CustomResult]> {
    SwifQL

        /// your complex query here

        .execute(.psqlEnvironment, on: req)
        .all() // or explicit .all(decoding: CustomResult.self)
        // .first()  // or explicit .first(decoding: CustomResult.self)
        // .count()
}