S3 instead of Ceph

[VannTen]

User stories

• As a Thoth developer, I need to understand that ceph is used only for its S3
  API
• As a Thoth operator, I need to know I can deploy Thoth using any S3
  implementation

Acceptance criterias

• thoth-storages no longer reference Ceph (-> S3)
• Other thoth components are updated to use the new names (for those part of
  the thoth.storages public interface)

Since we use Ceph as S3 store only (AFAICT), can we use consistently S3 instead
of Ceph in the code and documentation ?

In the documentation or in the code, using ceph as a name does make it clear
that we're using an object store, and targeting the S3 API (since Ceph has other
storages modes).

[VannTen]

/area documentation
/kind feature

[VannTen]

/kind cleanup
/remove-label area/documentation kind/feature

[VannTen]

/remove kind/feature area/documentation

[VannTen]

/remove kind/feature

[goern]

/triage needs-information

[VannTen]

Potential problems: - CephStore is in `__all__` (__init__.py), so changing it is probably a breaking change. I think at least thoth-station/slo-reporter use it, might be other, I just did a grep on the repos I had cloned.

[VannTen]

Relevant: code external to storages that would need modification).

https://github.com/search?q=org%3Athoth-station+-repo%3Athoth-station%2Fstorages+CephStore&type=code
https://github.com/search?q=org%3Athoth-station+-repo%3Athoth-station%2Fstorages+thoth.storages.ceph&type=code
(around 35 hits)

[VannTen]

/sig stack-guidance

[sesheta]

Issues needing reporter input close after 60d,

If there is new input, reopen with /reopen.