When a firewall or other network interference prevents the client from connecting to Firestore, weird things can happen. In some cases, they are able to perform an OAuth sign-in, but a failure occurs during the onboarding step where they set their handle. If they try this with different handles, it can result in multiple user records with the same UID being created in the users collection.

We should implement the "firewall detected" message to reduce support effort for users with these connectivity issues, as they can be a lot of work to troubleshoot.

Example user issue: https://feedback.flux.ai/admin/feedback/bugreports/p/username-shows-yomama-should-be-xboxusr666?boards=bugreports

Feature spec: https://coda.io/d/Firewall-detected_dDkP2hJPBbZ/Firewall-detected_su6gV#_luc9d