metadata is too much data to be useful to an end user, meanwhile err is getting clobbered.
before
```
Error: Unable to complete backup
Message: <nil>
Metadata:{"assist_bases":"0","backup_id":"40940295-3611-42fb-ac27-5b80691ba793","base_backup_id":"832fff09-4988-4a3e-a0d0-4e51b197ea14","can_use_metadata":"true","can_use_previous_backup":"true","categories":"[Chats]","clues_trace":"c3bbd0e6","collection_count":"2","disable_assist_backup":"false","incremental":"true","merge_bases":"1","repo_ref":"fb8afbaa-e94c-4ea5-8a8a-24aff04d7874/chats/311d2a89-4c80-4da4-86ef-a08d8d6f0f94/chats/19:311d2a89-4c80-4da4-86ef-a08d8d6f0f94_817c2506-de4a-4795-971e-371ea75a03ed@unq.gbl.spaces","resource_owner_id":"311d2a89-4c80-4da4-86ef-a08d8d6f0f94","resource_owner_name":"rfinders@10rqc2.onmicrosoft.com","resource_owner_selected":"rfinders@10rqc2.onmicrosoft.com","service":"service(5)","tenant_id":"fb8afbaa-e94c-4ea5-8a8a-24aff04d7874"}
```
after
```
Error: Unable to complete backup
Cause: running backup: merging details: merging merge backup base details: getting updated info for entry: getting previous item location: unable to extract LocationRef from RepoRef
```
---
#### Does this PR need a docs update or release note?
- [x] ⛔ No
#### Type of change
- [x] 🧹 Tech Debt/Cleanup
#### Test Plan
- [x] 💪 Manual
cc24f9b6e7