Database cluster still has `interactive` database and user

[StevenMaude]

While looking around to learn more about job-server's database setup, I noticed that the same cluster still has an interactive database, and an associated user.

I believe this is from the original OpenSAFELY Interactive deployment, before Interactive was moved into job-server.

There is a backup of the data in the Digital Ocean object store.

Based on that backup, the storage used by the interactive database is probably tiny, but if we no longer need it, it is perhaps a candidate for cleaning up.

[StevenMaude]

I checked this with Team RAP.

[StevenMaude]

This needs someone with delete permissions on Digital Ocean to remove the user.

Digital Ocean have instructions on this process.