Improve Firebase Functions cold start times #4356
Description
Firebase functions for groups have very bad cold start times (ie. for viewing members in groups, clicking join group link, etc).
Looks like this issue was fixed by Google a while ago:
- https://issuetracker.google.com/issues/158014637?pli=1
- feat(fs): preferRest app option for Firestore firebase/firebase-admin-node#1901
We should enable these fixes.
It is currently not enabled by default (firebase/firebase-tools#6520), but for our use case I think we should enable it.