Change the way page_count is counted

[gaato]

Summary

Changed the way Pagination.page_count is counted.

The documentation says a zero-indexed value, but since this is a count, not an index, it is more appropriate to count it normally.

It is not correct that page_count is -1 when there are no pages (which is not possible with the current code).

Did the previous page_count represent the index of the last page (0-based)?

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...)

[krittick]

page_count is intended to be zero-indexed and is primarily used internally as such. Any values displayed to users are already converted to a more readable one-indexed value, but we should still be referring to it internally as a zero-indexed field for simplicity.

There are also better ways to handle the situation where there are no pages and page_count shows as -1 instead of changing the entire attribute indexing.

[krittick]

Note that there is development in progress to move a lot of Paginator attributes to properties, and having different page_count and page_index properties is part of that work. It's not a bad idea itself, but shouldn't be done as a separate breaking PR without that context around it.

X

[krittick]

As an aside, the use case you mentioned where page_count shows as -1 when there are no pages has been addressed in the fixes included in #1227.