ARTIFACT table doesn't get cleaned when a plan is moved to a different project

I was able to reproduce this behavior. Here are the steps:

confirmed the deletion from the ARTIFACT table is a bug after plans have been moved. Below are the steps I used to reproduce the issue.

1. Performed a few builds in 2 different plans (each having artifacts configured) in 2 different projects.
2. Verified the records were in the ARTIFACT table
3. Deleted one result manually through the Bamboo UI. Bamboo correctly removed the record from ARTIFACTS table.
4. Configured build expiry, and it also correctly removed the record from ARTIFACT table.
5. Moved one of the plans from its project to the other project with a new key. Confirmed old ARTIFACT record was there (using the original PLAN_KEY).
6. Deleted the moved result and plan, but the ARTIFACT record still remained there and was not deleted.

(Maybe we should update the PLAN_KEY on the ARTIFACT table when a plan is moved?)