Add signposting to the end of truncated pagination

[jonoaldersonwp]

For logged-out users, we cut off all pagination at 49 pages. This aims to reduce the performance impact of requests to deeply paginated URLs.

This has an unfortunate side-effect of making it seem like there are only 49 pages of any given result type. This may confuse users.

As such, when a logged-out user requests page 49 of a series (which would otherwise have had more than 49 pages), we should show a "Log in to see more" component.

This may require some minimal design and copy considerations.