Add support for mass transfers

[ajjswift]

Pelican should add reliable support for the mass transfer of servers between nodes, instead of having to transfer them one-by-one.

[lancepioch]

What kind of scale are we talking about here, how many servers are you typically transferring and how often?

[ajjswift]

Entire nodes, not hugely often.

Useful for decommissioning old nodes to upgrade to newer hardware. Currently it's a pain having to transfer one-by-one.

[starrider346]

Node transfer seems like a really useful thing.

[HerrSammyDE]

What kind of scale are we talking about here, how many servers are you typically transferring and how often?

@lancepioch

from an entrepreneurial perspective:

We had transferred a few hundred servers (just under 1k) from Datacenter A to Datacenter B. We had to write something ourselves so that we didn't have to transfer each server independently.

So it would be very cool!