We don't have a database method to remove the SessionItem, because there was no need to remove it explicitly. The item record is removed by the DynamoDB TTL. We don't have any device "logout" for implementing the remove method and removing it explicitly from the tunnelbroker side.
Now we need to remove the SessionItem record from the database explicitly in tests (we'll insert, check and remove).
Realizing this will change the version of ws that is imported here. In fact we're already importing a newer version (7.5.9) than our version of express-ws uses (5.2.3), but it looks like we only use it for Flow types so it's okay