Third item of the v1.0.6 backlog. The v1.0.5.1 hotfix surfaced that two
email paths in-tree read *different* env vars for the same configuration:
internal/email/sender.go internal/services/email_service.go
SMTP_USERNAME SMTP_USER
SMTP_FROM FROM_EMAIL
SMTP_FROM_NAME FROM_NAME
The hotfix worked around it by exporting both sets in `.env.template`.
This commit reconciles them onto a single schema so the workaround can
go away.
Changes
* `internal/email/sender.go` is now the single loader. The canonical
names (`SMTP_USERNAME`, `SMTP_FROM`, `SMTP_FROM_NAME`) are read
first; the legacy names (`SMTP_USER`, `FROM_EMAIL`, `FROM_NAME`)
stay supported as a migration fallback that logs a structured
deprecation warning ("remove_in: v1.1.0"). Canonical always wins
over deprecated — no silent precedence flip.
* `NewSMTPEmailSender` callers keep working unchanged; a new
`LoadSMTPConfigFromEnvWithLogger(*zap.Logger)` variant lets callers
opt into the warning stream.
* `internal/services/email_service.go` drops its six inline
`os.Getenv` reads and delegates to the shared loader, so
`AuthService.Register` and `RequestPasswordReset` now see exactly
the same config as the async job worker.
* `.env.template`: the duplicate (SMTP_USER + FROM_EMAIL + FROM_NAME)
block added in v1.0.5.1 is removed — only the canonical SMTP_*
names ship for new contributors.
* `docker-compose.yml` (backend-api service): FROM_EMAIL / FROM_NAME
renamed to SMTP_FROM / SMTP_FROM_NAME to match the canonical schema.
* No Host/Port default injected in the loader. If SMTP_HOST is
empty, callers see Host=="" and log-only (historic dev behavior).
Dev defaults (MailHog localhost:1025) live in `.env.template`, so
a fresh clone still works; a misconfigured prod pod fails loud
instead of silently dialing localhost.
Tests
* 5 new Go tests in `internal/email/smtp_env_test.go`: empty-env
returns empty config; canonical names read directly; deprecated
names fall back (one warning per var); canonical wins over
deprecated silently; nil logger is allowed.
* Existing `TestLoadSMTPConfigFromEnv`, `TestSMTPEmailSender_Send`,
and every auth/services package remained green (40+ packages).
Import-cycle note: the loader deliberately lives in `internal/email`,
not `internal/config`, because `internal/config` already depends on
`internal/email` (wiring `EmailSender` at boot). Putting the loader in
`email` keeps the dependency flow one-way.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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