feat: expose immutable postbox file references

src/govoplan_files/backend/storage/files.py

@@ -731,6 +731,21 @@ def read_asset_bytes(session: Session, asset: FileAsset) -> tuple[bytes, FileVer
     return read_verified_blob_bytes(blob, backend=backend), version, blob
 
 
+def read_asset_version_bytes(
+    session: Session,
+    asset: FileAsset,
+    version_id: str,
+) -> tuple[bytes, FileVersion, FileBlob]:
+    version = session.get(FileVersion, version_id)
+    if version is None or version.file_asset_id != asset.id:
+        raise FileStorageError("File version not found")
+    blob = session.get(FileBlob, version.blob_id)
+    if blob is None or blob.tenant_id != asset.tenant_id:
+        raise FileStorageError("File blob not found")
+    backend = get_storage_backend()
+    return read_verified_blob_bytes(blob, backend=backend), version, blob
+
+
 def share_file(
     session: Session,
     *,