Add auto-unseal using Open Telekom Cloud KMS feature

[keviiin38]

As opened in hashicorp/vault#20338, I'd like to use Open Telekom Cloud KMS in order to auto-unseal Vault.

Started a fork in order to try to implement this feature: keviiin38/go-kms-wrapping#add-opentelekomcloudkms-wrapper

[baurmatt]

Hey @keviiin38, what's the state of your fork/implementation? We're interested in this feature as well but for OpenStack in general.