fix(workflow): pass renamed backend build-args for syncstorage-rs 0.23+

[tmiland-labs]

Problem

Since syncstorage-rs 0.23.x, the upstream Dockerfile renamed its build args: DATABASE_BACKEND was split into SYNCSTORAGE_DATABASE_BACKEND and TOKENSERVER_DATABASE_BACKEND, both defaulting to spanner.

This workflow still passes only the old DATABASE_BACKEND=mysql arg, which the new Dockerfile silently ignores. The result is a Spanner build of the app image. At startup the Spanner manager rejects the mysql:// URL configured by the compose file and the container panics:

thread 'main' panicked at syncserver/src/main.rs:57:55:
... Invalid database url: mysql://... status: 500

(raised in syncstorage-spanner/src/manager/session.rs:74, spanner_database_name())

Confirmed against the 0.23.3 build published by this repo's weekly cron — every current :latest app image is broken and no deployment using mysql:// URLs can start.

Fix

Pass the two renamed args in addition to the old one, so builds of pre-0.23 tags (which read DATABASE_BACKEND) and 0.23+ tags (which read the new args) both get the mysql backend:

build-args: |
  DATABASE_BACKEND=${{ env.DATABASE_BACKEND }}
  SYNCSTORAGE_DATABASE_BACKEND=${{ env.DATABASE_BACKEND }}
  TOKENSERVER_DATABASE_BACKEND=${{ env.DATABASE_BACKEND }}

Verification

• Built with the patched workflow (syncstorage-rs-mysql-latest, upstream tag 0.23.3, amd64 + arm64): image starts cleanly with SYNC_TOKENSERVER__* mysql URLs, /__heartbeat__ returns 200, tokenserver endpoint answers, real Firefox client syncs successfully.
• Side note: 0.23.3 defaults MYSQLCLIENT_PKG=libmariadb-dev-compat, so the existing arm64 libmysqlclient-dev sed is a no-op there (kept as-is for older tags).

[skazi0]

#20 is waiting since March :o|

[tmiland-labs]

Thanks for the nudge @skazi0 — your analysis in #20 was spot on: the 0.23.x Dockerfile renamed/split the args, and passing only the old DATABASE_BACKEND silently produces Spanner builds that panic with Invalid database url. We independently hit the same wall (see #24) and kept the old arg as well so pre-0.23 tags still build.

While this sits in review: our fork already publishes working images — ghcr.io/tmiland/firefox-sync:syncstorage-rs-mysql-latest (syncstorage-rs 0.23.3, mysql backend) has been running in production on our server since 2026-09-07 (nginx + real Firefox clients syncing), and the fork's init image also carries the tokenserver db init fix (#23). So if you need a working 0.23.x deployment today, the fork is ready to use.