[lib][keyserver] Handle invalid CSAT in BlobOperationResult

Summary:
Part of ENG-9526.

Depends on D13957, D13960

Test Plan: Manual testing with mocked invalid access token

Reviewers: kamil, varun, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13988