doc: migrate gitlab to new k8s cluster

Is there any guidance on how to move a gitlab deployment to a new k8s cluster? I could not find it in the documentation - but perhaps I overlooked.

There are some generated items, like encryption keys/secrets that need to remain the same. Is there any documentation on which ones exactly? Would a new chart be deployed with these secrets filled in the values.yaml ?

I'm using an external DB and I'm working on the assumption that I can, either backup/restore gitaly data (using the backup-utility), or restore the physical files from a PV dump or rsync the data over) - I'm not too worried about that.