Merge branch 'fix/backup-chunked-storage' into release/v1.39.2

docs/api/openapi.yaml

@@ -20804,11 +20804,19 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/ErrorEnvelope"
+        "409":
+          description: The stored copy was replaced by a newer one while it was being read. `meta.errorCode` = `backup_changed`.
+            Nothing was changed; start again to use the new copy.
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ErrorEnvelope"
         "422":
           description: "The stored copy could not be opened: either the key that wrote it is no longer in `ENCRYPTION_KEYS` (a
             rotation that dropped the legacy entry too early), or the stored bytes are not the ones that were written (a
-            stored piece missing, moved, altered, taken from another copy, or the copy cut short). Every piece is
-            checked before any of the copy is read. `meta.errorCode` = `backup.payload.undecryptable`. Nothing was
+            stored piece missing, moved, altered, taken from another copy, or the copy cut short), or the row holds both
+            a single value and pieces, which only an older release writing to it after an upgrade produces. Every piece
+            is checked before any of the copy is read. `meta.errorCode` = `backup.payload.undecryptable`. Nothing was
             changed."
           content:
             application/json:
@@ -20865,8 +20873,9 @@ paths:
         "404": *a51
         "409":
           description: A restore of the same account is already queued or running (`meta.errorCode` = `backup.restore.active`,
-            `meta.jobId` names it), or a request under the same `Idempotency-Key` is still in flight. Nothing was
-            changed.
+            `meta.jobId` names it), the stored copy was replaced by a newer one while it was being checked
+            (`meta.errorCode` = `backup_changed`), or a request under the same `Idempotency-Key` is still in flight.
+            Nothing was changed.
           content:
             application/json:
               schema: