Add ADR for Rook

[b1-lender]

This PR adds an ADR regarding Rook.
fixes: SovereignCloudStack/issues#515

[fkr]

Suggested change

	**Environment**: Cephadm is better suited for traditional or standalone environments. Conversely, Rook is tailored for Kubernetes. That being said, it's important to note that the current state of resource deployment and management on Kubernetes within the reference implementation is still in its early stages. This would make Rook one of the first components to utilise Kubernetes in OSISM.
	**Environment**: Cephadm is better suited for traditional or standalone environments. Conversely, Rook is tailored for Kubernetes. That being said, it's important to note that the current state of resource deployment and management on Kubernetes within the IaaS reference implementation is still in its early stages. This would make Rook one of the first components to utilise Kubernetes in OSISM.

Furthermore Keycloak is already being deployed to the kubernetes, so I'm not sure wether the statement of the Rook being the first holds. Nevertheless, it is early stages, so that of course is correct.

[b1-lender]

I'd say that one of the first components states that Rook isn't the very fist component on Kubernetes.

[fkr]

Only couple of minor corrections.

[fkr]

Thanks @b1-lender - this reads well. Since there are quite references to OSISM and its future direction (re. kubernetes), I think, it is important that @berendt comments.
For the formal correctness, I think it makes sense that someone like @markus-hentsch or @mbuechse reviews it, they're good with that :)

[mbuechse]

ERROR: duplicates found: scs-0118-v1-rook-decision.md, scs-0118-v1-taxonomy-of-failsafe-levels.md

Why was this merged when the test failed so blatantly?

[b1-lender]

I didn't pay enough attention because merging was possible.
What would be the preferred way to resolve this error, simply a new PR with the fix?

[tonifinger]

I didn't pay enough attention because merging was possible. What would be the preferred way to resolve this error, simply a new PR with the fix?

I already created a PR to fix this, because it is currently blocking a PR I'm working on: #767
Could i ask you to review it ?