Provide opportunity for users to lookup currently deployed metal-stack version

[Gerrit91]

At the moment, a user cannot find out on his own which metal-stack version is deployed in an environment. It is only known by the people who deploy the software (operators). A user can query the metal-api version endpoint, but it is not possible to deduce the actual metal-stack release from that.

However, it would be very useful for users to have this information such that they can automatically pull and use compatible clients to access the metal-api.

Question is if it does make sense to make the metal-stack version obtainable because operators can theoretically diverge from metal-stack releases with individual components such that there is no guarantee anymore that clients belong together.

Probably relates to metal-stack/metalctl#5.

[majst01]

Proposal:

• metalctl update do checks against metal-api/version endpoint from which release this was deployed, fetching metalctl will then use the version specified in the metal-stack/release

same applies for cloudctl

[majst01]

should be also exposed via the version endpoint

[Gerrit91]

But the same metal-api/version can be used over many releases of metal-stack.

Even if it's a bit weird, I another option is that the metal-api get's a flag for the release version and this can be injected through deployment.

[Gerrit91]

Done with metal-stack/metal-api#546,