Support bootstrapping demo users in main DB setup script, if appropriate

[stevejalim]

This is so that we can boostrap SSO users on the demo servers on Cloud Run.

This approach is a lot simpler, cleaner and more build-time efficient than doing a multi-stage container build in Cloud Build, but it does add to the complexity of that sync-all script...

• I used an AI to write some of this code.

Issue / Bugzilla link

15375

Testing

• [email protected],[email protected] ./bin/sync-all.sh - to see demo users bootstrapped
• [email protected],[email protected] ./bin/sync-all.sh again, to see what happens if they already exist
• ./bin/sync-all.sh to confirm demo users are not bootstrapped if the env var isn't there

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.68%. Comparing base (d3f7f52) to head (67cb4b9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15394      +/-   ##
==========================================
+ Coverage   78.66%   78.68%   +0.01%     
==========================================
  Files         156      156              
  Lines        8165     8171       +6     
==========================================
+ Hits         6423     6429       +6     
  Misses       1742     1742              

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[robhudson]

👢