feat(kms): Add KMS under beta

[JanStern]

Description

relates to #934

KMS has been added to the CLI. Now the following commands exist:

• key (create, delete, import, list, restore, rotate)
• key ring (create, delete, list)
• version (destroy, disable, enable, list, restore)
• wrapping key (create, destroy, list)

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see e.g. here)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

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Important Decisions

The CLI implementation of KMS reflects the state of the API, which includes some seemingly unfinished decisions.

1. The Region doesn't matter even though it exists: Every API Endpoint has the region as a required attribute. However, the value is currently meaningless. All requests have the same result no matter what the region is. Still I haven't removed/mocked the structure in the code since I assume that in the future KMS will be region specific.
2. Backend is a fixed but required value: When creating a wrapped key or a key, backend is a required body parameter that is currently only "software". Here following the same argument as before I have made it a flag in anticipation of future updates.
3. I recommend extra detail to Importing a Key: Following this example I experimented with the key importing and tried to import an invalid key. I did encode random text in base64 and it was accepted. It created a new key version but with the status "Errors existing", which feels wrong. Nonetheless, I don't think that the formatting checks in the CLI should be stricter. (I just wanted to draw attention to that)

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Hope this actually helps and huge thanks to whomever tries to tackle this monster merge.