Migration: Set default arch values for boot sets with no arch field

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Marked PATCH session status endpoint to be ignored by the CLI.
 - Eliminate redundancies in API spec by defining `V2SessionNameOrEmpty` schema.
 - Refactor `validate_boot_sets` function into multiple functions to make it easier to understand.
+- During migration to this BOS version, for boot sets with no `arch` field, add the field with its
+  default value.
 
 ### Fixed
 - When validating boot sets, check all boot sets for severe errors before returning only warnings

src/bos/server/migrations/sanitize.py

@@ -28,7 +28,7 @@
 import string
 
 from bos.common.tenant_utils import get_tenant_aware_key
-from bos.server.controllers.v2.boot_set import HARDWARE_SPECIFIER_FIELDS
+from bos.server.controllers.v2.boot_set import DEFAULT_ARCH, HARDWARE_SPECIFIER_FIELDS
 from bos.server.schema import validator
 
 from .db import TEMP_DB, delete_component, delete_session, delete_template
@@ -196,6 +196,10 @@ def sanitize_bootset(bsname: str, bsdata: dict) -> str|None:
     # be stored inside the boot set under the current API spec
     bsdata.pop("name", None)
 
+    # If the arch field is not present, set it to its default value
+    if "arch" not in bsdata:
+        bsdata["arch"] = DEFAULT_ARCH
+
     # Remove any fields that are no longer in the spec
     bad_fields = [ field for field in bsdata if field not in validator.boot_set_fields ]
     for field in bad_fields: