Improve sample files

[jacalata]

1. show a way to read credentials better than the command line
2. fix the incorrect 'paging' used in several samples (server.views.populate_image gives outdated image even with refresh to the datasource #1531)
3. check the samples as a whole for comprehensive coverage

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. If this is still relevant, please comment to keep it open.

[github-actions]

Closing due to inactivity. If this is still relevant, please reopen or file a new issue.