rbd: add aws-sts-metdata encryption type

With Amazon STS and kubernetes cluster is configured with
OIDC identity provider, credentials to access Amazon KMS
can be fetched using oidc-token(serviceaccount token).
Each tenant/namespace needs to create a secret with aws region,
role and CMK ARN.
Ceph-CSI will assume the given role with oidc token and access
aws KMS, with given CMK to encrypt/decrypt DEK which will stored
in the image metdata.

Refer: https://docs.aws.amazon.com/STS/latest/APIReference/welcome.html
Resolves: #2879

Signed-off-by: Rakshith R <rar@redhat.com>

vendor/github.com/aws/smithy-go/document/doc.go

@@ -0,0 +1,12 @@
+// Package document provides interface definitions and error types for document types.
+//
+// A document is a protocol-agnostic type which supports a JSON-like data-model. You can use this type to send
+// UTF-8 strings, arbitrary precision numbers, booleans, nulls, a list of these values, and a map of UTF-8
+// strings to these values.
+//
+// API Clients expose document constructors in their respective client document packages which must be used to
+// Marshal and Unmarshal Go types to and from their respective protocol representations.
+//
+// See the Marshaler and Unmarshaler type documentation for more details on how to Go types can be converted to and from
+// document types.
+package document