Migrate RAK2245 from TTN to TheThingsStack v3

[bluejedi]

@ecosoph

I was a bit irritated by the documentation that suggests the EUI is kind of optional now ( Gateway EUI (if your gateway has an EUI).

If you have any suggestions for improving or fixing the documentation see:

@bluejedi

If you find an issue in the Things Stack V3 documentation then please report the issue in The Things Stack documentation repository on Github so that it can be fixed.