feat: govern shared campaign artifact storage

src/govoplan_campaign/backend/sending/jobs.py

@@ -16,6 +16,10 @@ from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from govoplan_core.core.notifications import NotificationDispatchRequest, notification_dispatch_provider
+from govoplan_core.core.object_storage import (
+    StorageBackendError,
+    configured_storage_backend,
+)
 from govoplan_core.audit.logging import audit_event
 from govoplan_core.security.redaction import redact_secret_values
 from govoplan_core.settings import settings as core_settings
@@ -53,7 +57,7 @@ from govoplan_campaign.backend.sending.postbox_delivery import (
     PostboxChannelOutcome,
     deliver_campaign_job_to_postboxes,
 )
-from govoplan_campaign.backend.runtime import get_registry
+from govoplan_campaign.backend.runtime import get_registry, get_settings
 from govoplan_campaign.backend.integrations import (
     ImapAppendError,
     ImapConfigurationError,
@@ -2389,6 +2393,17 @@ def _verify_eml_evidence(job: CampaignJob, payload: bytes) -> None:
 
 
 def _load_eml_bytes_for_job(job: CampaignJob) -> bytes:
+    if job.eml_storage_key:
+        try:
+            payload = configured_storage_backend(
+                get_settings() or core_settings
+            ).get_bytes(job.eml_storage_key)
+        except StorageBackendError as exc:
+            raise SendJobError(
+                f"Generated EML object could not be read for job {job.id}: {exc}"
+            ) from exc
+        _verify_eml_evidence(job, payload)
+        return payload
     if job.eml_local_path:
         path = Path(job.eml_local_path)
         if not path.exists():
@@ -2396,7 +2411,7 @@ def _load_eml_bytes_for_job(job: CampaignJob) -> bytes:
         payload = path.read_bytes()
         _verify_eml_evidence(job, payload)
         return payload
-    raise SendJobError("Only local EML paths are supported for sending in this implementation step")
+    raise SendJobError("Generated EML evidence is not available for this job")
 
 
 def _load_eml_for_job(job: CampaignJob):