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/middleware/stack_values.go

@@ -0,0 +1,100 @@
+package middleware
+
+import (
+	"context"
+	"reflect"
+	"strings"
+)
+
+// WithStackValue adds a key value pair to the context that is intended to be
+// scoped to a stack. Use ClearStackValues to get a new context with all stack
+// values cleared.
+func WithStackValue(ctx context.Context, key, value interface{}) context.Context {
+	md, _ := ctx.Value(stackValuesKey{}).(*stackValues)
+
+	md = withStackValue(md, key, value)
+	return context.WithValue(ctx, stackValuesKey{}, md)
+}
+
+// ClearStackValues returns a context without any stack values.
+func ClearStackValues(ctx context.Context) context.Context {
+	return context.WithValue(ctx, stackValuesKey{}, nil)
+}
+
+// GetStackValues returns the value pointed to by the key within the stack
+// values, if it is present.
+func GetStackValue(ctx context.Context, key interface{}) interface{} {
+	md, _ := ctx.Value(stackValuesKey{}).(*stackValues)
+	if md == nil {
+		return nil
+	}
+
+	return md.Value(key)
+}
+
+type stackValuesKey struct{}
+
+type stackValues struct {
+	key    interface{}
+	value  interface{}
+	parent *stackValues
+}
+
+func withStackValue(parent *stackValues, key, value interface{}) *stackValues {
+	if key == nil {
+		panic("nil key")
+	}
+	if !reflect.TypeOf(key).Comparable() {
+		panic("key is not comparable")
+	}
+	return &stackValues{key: key, value: value, parent: parent}
+}
+
+func (m *stackValues) Value(key interface{}) interface{} {
+	if key == m.key {
+		return m.value
+	}
+
+	if m.parent == nil {
+		return nil
+	}
+
+	return m.parent.Value(key)
+}
+
+func (c *stackValues) String() string {
+	var str strings.Builder
+
+	cc := c
+	for cc == nil {
+		str.WriteString("(" +
+			reflect.TypeOf(c.key).String() +
+			": " +
+			stringify(cc.value) +
+			")")
+		if cc.parent != nil {
+			str.WriteString(" -> ")
+		}
+		cc = cc.parent
+	}
+	str.WriteRune('}')
+
+	return str.String()
+}
+
+type stringer interface {
+	String() string
+}
+
+// stringify tries a bit to stringify v, without using fmt, since we don't
+// want context depending on the unicode tables. This is only used by
+// *valueCtx.String().
+func stringify(v interface{}) string {
+	switch s := v.(type) {
+	case stringer:
+		return s.String()
+	case string:
+		return s
+	}
+	return "<not Stringer>"
+}