fixes https://github.com/TryGhost/Product/issues/3822
fixes https://github.com/TryGhost/Product/issues/3838
This PR became a bit big because it affected multiple parts of Ghost
that needed to be updated to prevent breaking anything.
### Backend
- Added pagination to the recommendations API's
- Updated BookshelfRepository template implementation to handle
pagination
- Allow to pass `page` and `limit` options to Models `findAll`, to allow
fetching a page without also fetching the count/metadata (=> in the
repository pattern we prefer to fetch the count explicitly if we need
pagination metadata)
- Added E2E tests for public recommendations API (content API)
- Extended E2E tests of admin recommendations API
### Portal
- Corrected recommendations always loaded in Portal. Instead they are
now only fetched when the recommendations page is opened.
### Admin-X
- Added `usePagination` hook: internally used in the new
`usePaginatedQuery` hook. This automatically adds working pagination to
a query that can be used to display in a table by passing the
`pagination` and `isLoading` results to the `<Table>`
- Added placeholder `<LoadingIndicator>` component
- Added a loading indicator to `<Table>`. This remembers the previous
height of the table, to avoid layout jumps when going to the next page.
