[Task] Create backend command to transfer work sessions from one user to another

[mradamcox]

Describe the task
I just need a good, clean way to do this. Doesn't need to be publicly accessible. The use cases are:

1. Someone has performed work on a different sign in and wants to transfer the sessions over
   • This is main just for me, so admin sessions can be transferred to acfc
2. Someone has created a new account with new email, and wants their old work to be transferred over
   • In this case it would be nice to have an extra flag to deactivate the old account

Importantly, other derivatives from the session must be transferred as well. GCPs, for example. Anything else?

Completion criteria
Must be able to do the tasks above via command line. Should also be able to provide a pk or list of pks for specific sessions to transfer.