we are migrating our project from gcm to firebase. In the google integrations page in the portal, I can see only 1 field for the "GCM Server API Key". Firebase works when I post the firebase key there but then gcm doesn't work anymore and other way around (gives 401). How can we perform the migration that both work in parallel until all clients are updated?
To answer myself:
I see that google has an "old serverkey" in the firebase console that is the same as for gcm. Now it works for both.