Improved user management for customers with large number of users

Created by: mike-r-mclaughlin

Requested by: https://github.com/sourcegraph/accounts/issues/6716

Feature request description

• Add pagination to the User Management page in site admin (/site-admin/users).
• Show the date joined, and the date last used
• Allow multi-selection of users for bulk actions
  • Action for deleting users

Is your feature request related to a problem? If so, please describe.

When customers have large numbers of users (100s or 1000s), it's very difficult to manage those users in the current view. Pagination would help (i.e., not just "show more" but having pages).

Pagination will help with scripts that customers write using APIs as well. Currently, the only API available is query users and that API requires you to make one API call to get all users (i.e., there is a first parameter that allows you to get the "first x users"; but, there is no way to know if there are more users after that).