# What this PR does
Allow creating multiple mobile devices with same `registration_id` for
different users (multi-stack support)
## Which issue(s) this PR fixes
https://github.com/grafana/oncall/issues/3452
## Checklist
- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)
Some tests (particularly when there are schedules and shifts involved)
depend on generated usernames being unique (we randomly get [CI
errors](https://github.com/grafana/oncall/actions/runs/6812435056/job/18524768961#step:5:676)
because of this). Although username field is not required to be unique,
I think it makes sense for testing purposes to enable this (and when a
duplicated username is needed in a test, make that explicit).
