This commit adds support for KMS master key versions.
Now, MinIO stores any key version information returned by the
KMS as part of the object metadata. The key version identifies
a particular master key within a master key ring. When encrypting/
generating a DEK, MinIO has to remember the key version - similar to
the key name. When decrypting a DEK, MinIO sends the key version to
the KMS such that the KMS can identify the exact key version that
should be used to decrypt the object.
Existing objects don't have a key version. Hence, this field will
be empty.
Signed-off-by: Andreas Auernhammer <github@aead.dev>
