## Context
The email-roundtrip-monitor CronJob injected `BREVO_API_KEY` and
`EMAIL_MONITOR_IMAP_PASSWORD` as inline `env { value = var.xxx }` —
Terraform read them from Vault at plan time and embedded them in the
generated CronJob spec. Anyone with `kubectl describe cronjob` (or
pod-event read) in the `mailserver` namespace could read both secrets
verbatim.
The two upstream Vault entries are not flat strings:
- `secret/viktor` → `brevo_api_key` = base64(JSON({"api_key": "..."}))
- `secret/platform` → `mailserver_accounts` = JSON({"spam@viktorbarzin.me": "<pw>", ...})
A plain ESO `remoteRef.property` can traverse one level of JSON but
cannot base64-decode the wrapper or index a map key that contains `@`.
So the ExternalSecret pulls the raw Vault values and the rendered K8s
Secret is produced via ESO's `target.template` (engineVersion v2, sprig
pipeline `b64dec | fromJson | dig`). `mergePolicy` defaults to Replace,
so only the transformed `BREVO_API_KEY` / `EMAIL_MONITOR_IMAP_PASSWORD`
keys land in the K8s Secret — the raw wrapped inputs never reach it.
## This change
1. New `kubernetes_manifest.email_roundtrip_monitor_secrets` rendering
an `external-secrets.io/v1beta1` ExternalSecret into a K8s Secret
named `mailserver-probe-secrets` via the `vault-kv` ClusterSecretStore.
2. CronJob's two `env { name=... value=var.xxx }` blocks replaced with
a single `env_from { secret_ref { name = "mailserver-probe-secrets" } }`.
3. Unused `brevo_api_key` / `email_monitor_imap_password` module
variables + their wiring in `stacks/mailserver/main.tf` removed.
`data "vault_kv_secret_v2" "viktor"` dropped (last consumer gone).
```
Before: After:
┌────────────┐ ┌────────────┐
│ Vault KV │ │ Vault KV │
└────┬───────┘ └────┬───────┘
│ (plan-time read) │ (runtime pull)
▼ ▼
┌────────────┐ ┌────────────┐
│ Terraform │ │ ESO ctrl │
│ state │ │ +template │
└────┬───────┘ └────┬───────┘
│ inline value= │ sprig b64dec | fromJson
▼ ▼
┌────────────┐ ┌────────────┐
│ CronJob │ <-- kubectl describe leaks! │ K8s Secret │
│ env[].value│ │ probe-sec │
└────────────┘ └────┬───────┘
│ env_from.secret_ref
▼
┌────────────┐
│ CronJob │
│ (no values │
│ in spec) │
└────────────┘
```
## Test Plan
### Automated
`terragrunt plan -target=...ExternalSecret -target=...CronJob`:
```
Plan: 1 to add, 1 to change, 0 to destroy.
+ kubernetes_manifest.email_roundtrip_monitor_secrets (ExternalSecret)
~ kubernetes_cron_job_v1.email_roundtrip_monitor
- env { name = "BREVO_API_KEY" ... }
- env { name = "EMAIL_MONITOR_IMAP_PASSWORD" ... }
+ env_from { secret_ref { name = "mailserver-probe-secrets" } }
```
`terragrunt apply --non-interactive` same targets:
```
Apply complete! Resources: 1 added, 1 changed, 0 destroyed.
```
`kubectl get externalsecret -n mailserver mailserver-probe-secrets`:
```
NAME STORE REFRESH INTERVAL STATUS READY
mailserver-probe-secrets vault-kv 15m SecretSynced True
```
`kubectl get secret -n mailserver mailserver-probe-secrets -o yaml`
exposes exactly two data keys (`BREVO_API_KEY`, `EMAIL_MONITOR_IMAP_PASSWORD`) —
both populated, 120 / 32 base64 chars, no raw `brevo_api_key_wrapped` /
`mailserver_accounts` keys.
`kubectl describe cronjob -n mailserver email-roundtrip-monitor`:
```
Environment Variables from:
mailserver-probe-secrets Secret Optional: false
Environment: <none>
```
(Previously the `Environment:` block listed both secrets with their raw
values.)
### Manual Verification
1. `kubectl create job --from=cronjob/email-roundtrip-monitor \
probe-test-$RANDOM -n mailserver`
2. `kubectl logs -n mailserver -l job-name=probe-test-... --tail=30`
expected:
```
Sent test email via Brevo: 201 marker=e2e-probe-...
Found test email after 1 attempts
Deleted 1 e2e probe email(s)
Round-trip SUCCESS in 20.3s
Pushed metrics to Pushgateway
Pushed to Uptime Kuma
```
3. `kubectl exec -n monitoring deploy/prometheus-prometheus-pushgateway \
-- wget -q -O- http://localhost:9091/metrics | grep email_roundtrip`
shows `email_roundtrip_success=1`, fresh timestamp, duration in range.
4. `kubectl delete job -n mailserver probe-test-...` to clean up.
Closes: code-39v
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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