For firebase authentication what's an easy way to pass the auth token to the server to do validated api requests?

I thought this would be straightforward but the best I could find was a strange nextjs library that does it on the edge and requires all manner of weird params.

What's the easiest way I could do this without getting overly complicated in the land of edge run times, etc? I'm at the point that I should just store the auth token in cookies and access it on the server that way.