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

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.