Previously we did only support ordering by a string or property path through Sort. In order to be able to express more type safe ordering expressions we introduce QSort as a subclass of Sort that is able to wrap QueryDSL OrderSpecifiers. To be able to separate the concerns of sorting via QueryDSL expressions better we introduce the AbstractPageRequest base class and QPageRequest as a special implementation that accepts a QSort or OrderSpecifiers for ordering.
Original pull request: #59.
PageRequest now actively prevents page sizes less than one. PageableHandlerMethodArgumentResolver falls back to default page size if it detects a page size less than one. It also rejects invalid default configuration using @PageableDefault.
So far, the PageImpl class returned 0 as total number of pages if set up from a plain List. This returns 1 now (as it should be). We've also adapted the hasNextPage() implementation to correctly calculate whether a next page is available.
