I have set up a Cloud Run service in GCP, and I added a Firebase hosting rewrite to point to it per these instructions.
This Cloud Run service proxies files from a GCP bucket to the client. These files can be large, and I'm adding byte ranging support. I have ranging working properly, and when I call the Cloud Run service directly, I get the response I expect. However, when I call it via the Firebase url rewrite, I discovered that the range request header is missing.
I've spent a couple of hours debugging and testing, and I believe that Firebase is what's dropping the header from the request.
Is there a header whitelist that I'm missing or something like that? I can't find anything in the docs about headers, other than how to override certain headers for caching purposes.