Here are some example persistent URLs you can use in the lab. They will stay constant for new sessions, even if the database is recreated.

https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-1&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-2&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-3&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-4&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-5&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-6&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-7&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-8&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-9&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-10&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-11&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-12&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-13&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-14&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-15&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-16&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-17&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-18&access_code_for_default_session=my_access_code
https://qlt.herokuapp.com/AssignVisitorToDefaultSession/?participant_label=PC-19&access_code_for_default_session=my_access_code

You should take these links, copy them for as many participants are in your session, and modify the participant_label parameter of each link. The above is just an example. You can use whatever naming scheme you would like to use, e.g. participant_label=PC-1, participant_label=PC-2, etc.

Note the parameter access_code_for_default_session. This is defined in your settings.py. You can change it as frequently as you'd like, to prevent unauthorized server access.