Devices can get out of sync between Synapse and MAS

[matrixbot]

This issue was originally created by @sandhose at matrix-org/matrix-authentication-service#2626.

The provisioning and deletion of devices is not exactly reliable (see #2625), which means sometimes the device list in Synapse gets out of sync with the one in MAS.

The long term solution may be to correctly model Matrix devices in MAS instead of relying solely on the scope for OAuth sessions and on a field in the compatibility sessions.

In the meantime, we should at least have a way to force a re-sync of the whole device list for a user, and maybe even regularly do that for all users.

[teutat3s]

I'm not sure how this was closed, but this is still important to me. On our HS this happened and the only workaround we found was a restart of mas.

[teutat3s]

Friendly ping to @sandhose

[sandhose]

This in the end is due to the unreliability of the job queue, which is being rewritten, see #2785