[ocis] Add S3NG consistency check

[tbsbdr]

Description

Assumptions

• S3ng
• snapshots

User Stories

• As an Admin I want an option to check if my backup is consistent so that I'm reassured that its complete and restorable.

• As an Admin I want an option to check if my data are consistent so that I'm reassured that there are not erroneous data.

Value

Acceptance Criteria

• add ocis command to check for consistency
  • the command checks the consistency of the decomposed fs, including the blob store
  • consistency check should not rely on a running ocis
  • symlinks/references can be followed / are not broken
  • referenced blob exists
  • no blobs without reference exists
  • check if file metadata are complete (xattr, msgpack...?)
  • if there are inconsistencies, return a list of the inconsistencies
• Note: search does not need to be checked; NATS does not need to be checked within the check

Definition of ready

• [ ] Everybody needs to understand the value written in the user story
• [ ] Acceptance criteria have to be defined
• [ ] All dependencies of the user story need to be identified
• [ ] Feature should be seen from an end user perspective
• [ ] Story has to be estimated
• [ ] Story points need to be less than 20

Definition of done

• Functional requirements
  • [ ] Functionality described in the user story works
  • [ ] Acceptance criteria are fulfilled
• Quality
  • [ ] Code review happened
  • [ ] CI is green (that includes new and existing automated tests)
  • [ ] Critical code received unit tests by the developer
• Non-functional requirements
  • [ ] No sonar cloud issues
• Configuration changes
  • [ ] The next branch of the ocis charts is compatible