Pagination dumps the previously checked users

The scenario: a user wants to add users on two separate pages. If they use the "Next" button to select a second user on a second page, the user selected on the first page is ignored.

Reproduce the scenario by selecting a user on one page, using the "Next" button, and selecting another user on the second page. Trace the pagination and user-selection entry points to find where selections are stored; done means both users remain selected and are included in the add-users operation.

Written by the indexing model from the issue text.