To add to @danbjoseph's recommendation, I would customize the QR codes to set the facility ID as the form metadata username. You can do this manually by scanning the code into Collect, manually setting the username by going to Settings > User and device identity > Form metadata, and then sharing the code back out from the device from Project management > Reconfigure with QR code > QR Code (you can use the share icon to share a file. Note that this flow is not as intuitive as it should be).
Alternately, you can script the QR code generation. There are a few examples of that on the forum and one using Python at https://github.com/getodk/pyodk/tree/master/examples#app-user-provisioning-script
Add a username field to your form as described in the metadata docs and that value will be pulled in.
For the interested, you can see a more complex example of using form metadata as a way to confiugre a form from @mathieubossaert in his post at ODK to collect species and habitats localities, as pressure and threats to ecosystems