Additional metrics about successful uploads #8522
Description
Is your proposal related to a problem?
Currently there is no way to determine from Thanos sidecar metrics when and if the last upload was successful.
Describe the solution you'd like
Add metric eg thanos_sidecar_last_successful_upload_timestamp_seconds that I can write alert for
This would cover connectivity issues and cases where upload credentials expire or are non usable
Describe alternatives you've considered
I looked at metrics exported by Thanos sidecar and didn't find usable one
Additional context
Checked last 0.39.2 version as well