Documentation on migrating DIY gateways #459

I was recently looking for information on how to migrate "old" DIY gateways built on/with Raspberry Pi and the Semtech packet forwarder. Building such gateways was a popular topic in the early TTN days.

Migrating such gateways to V3 is more than just changing a URL. You will likely want to build it from scratch using the Basic Station stack. Hence, I was wondering if a few notes and links about that topic in https://github.com/TheThingsNetwork/docs/blob/master/doc/content/the-things-stack/migrate-to-v3/migrate-gateways.md wouldn't be helpful for community members like myself.

One valuable resource I found was https://www.beyondlogic.org/lorawan-upgrading-to-basic-station-and-the-things-network-v3-stack/. I am not affiliated with the site but left a comment there.