Add support for image digests.

[jackson-chris]

The operator seems to not currently support image digests. It is common on openshift to take advantage of mirror registries to pull images which requires referencing images by their digests instead of tags.

This is a request to alter the operator to be able to support digests instead of tags.

[johscheuer]

The current solution would be to set allowTagOverride in the processSettings and then you can define your image with the tag. A rough example how that could look like can be found in the samples folder: https://github.com/FoundationDB/fdb-kubernetes-operator/blob/master/config/samples/cluster_local.yaml#L18. We already have an issue to keep track of that problem and hopefully we can close that work in the future: https://github.com/FoundationDB/fdb-kubernetes-operator/issues/387#issuecomment-812753652 or if you have interest in this feature PRs are welcome :)

[johscheuer]

I think with the image config that should be supported. If you still see any issues please reopen this issue.

[brownleej]

@johscheuer I tried using an image digest in some recent tests, and the syntax for them is slightly different in a way that the image configs don't support.

[johscheuer]

I think adding support for this should be pretty straightforward with the ImageConfig by just adding an additional field Digest. @blindenvy if you have some capacity and need this feature I'm happy to review those changes. I think the digest should have the highest "priority" if specified because that's the most precise way to define which image should be running. The. required changes are needed here: https://github.com/FoundationDB/fdb-kubernetes-operator/blob/main/api/v1beta1/foundationdbcluster_types.go#L2294-L2345 but I would suggest to wait until the v1bea2 CRD is merged and add the functionality there.

[jackson-chris]

I'm quite overloaded atm, but I will see if I can find some time to work on this. Thanks for the guidance on where to start.