rebase: Bump github.com/aws/aws-sdk-go-v2/service/sts

Bumps [github.com/aws/aws-sdk-go-v2/service/sts](https://github.com/aws/aws-sdk-go-v2) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/aws/aws-sdk-go-v2/releases)
- [Changelog](https://github.com/aws/aws-sdk-go-v2/blob/main/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-go-v2/compare/v1.20.0...service/s3/v1.21.0)

---
updated-dependencies:
- dependency-name: github.com/aws/aws-sdk-go-v2/service/sts
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/aws/aws-sdk-go-v2/internal/auth/scheme.go

@@ -0,0 +1,186 @@
+package auth
+
+import (
+	"context"
+	"fmt"
+
+	smithy "github.com/aws/smithy-go"
+	"github.com/aws/smithy-go/middleware"
+)
+
+// SigV4 is a constant representing
+// Authentication Scheme Signature Version 4
+const SigV4 = "sigv4"
+
+// SigV4A is a constant representing
+// Authentication Scheme Signature Version 4A
+const SigV4A = "sigv4a"
+
+// None is a constant representing the
+// None Authentication Scheme
+const None = "none"
+
+// SupportedSchemes is a data structure
+// that indicates the list of supported AWS
+// authentication schemes
+var SupportedSchemes = map[string]bool{
+	SigV4:  true,
+	SigV4A: true,
+	None:   true,
+}
+
+// AuthenticationScheme is a representation of
+// AWS authentication schemes
+type AuthenticationScheme interface {
+	isAuthenticationScheme()
+}
+
+// AuthenticationSchemeV4 is a AWS SigV4 representation
+type AuthenticationSchemeV4 struct {
+	Name                  string
+	SigningName           *string
+	SigningRegion         *string
+	DisableDoubleEncoding *bool
+}
+
+func (a *AuthenticationSchemeV4) isAuthenticationScheme() {}
+
+// AuthenticationSchemeV4A is a AWS SigV4A representation
+type AuthenticationSchemeV4A struct {
+	Name                  string
+	SigningName           *string
+	SigningRegionSet      []string
+	DisableDoubleEncoding *bool
+}
+
+func (a *AuthenticationSchemeV4A) isAuthenticationScheme() {}
+
+// AuthenticationSchemeNone is a representation for the none auth scheme
+type AuthenticationSchemeNone struct{}
+
+func (a *AuthenticationSchemeNone) isAuthenticationScheme() {}
+
+// NoAuthenticationSchemesFoundError is used in signaling
+// that no authentication schemes have been specified.
+type NoAuthenticationSchemesFoundError struct{}
+
+func (e *NoAuthenticationSchemesFoundError) Error() string {
+	return fmt.Sprint("No authentication schemes specified.")
+}
+
+// UnSupportedAuthenticationSchemeSpecifiedError is used in
+// signaling that only unsupported authentication schemes
+// were specified.
+type UnSupportedAuthenticationSchemeSpecifiedError struct {
+	UnsupportedSchemes []string
+}
+
+func (e *UnSupportedAuthenticationSchemeSpecifiedError) Error() string {
+	return fmt.Sprint("Unsupported authentication scheme specified.")
+}
+
+// GetAuthenticationSchemes extracts the relevant authentication scheme data
+// into a custom strongly typed Go data structure.
+func GetAuthenticationSchemes(p *smithy.Properties) ([]AuthenticationScheme, error) {
+	var result []AuthenticationScheme
+	if !p.Has("authSchemes") {
+		return nil, &NoAuthenticationSchemesFoundError{}
+	}
+
+	authSchemes, _ := p.Get("authSchemes").([]interface{})
+
+	var unsupportedSchemes []string
+	for _, scheme := range authSchemes {
+		authScheme, _ := scheme.(map[string]interface{})
+
+		switch authScheme["name"] {
+		case SigV4:
+			v4Scheme := AuthenticationSchemeV4{
+				Name:                  SigV4,
+				SigningName:           getSigningName(authScheme),
+				SigningRegion:         getSigningRegion(authScheme),
+				DisableDoubleEncoding: getDisableDoubleEncoding(authScheme),
+			}
+			result = append(result, AuthenticationScheme(&v4Scheme))
+		case SigV4A:
+			v4aScheme := AuthenticationSchemeV4A{
+				Name:                  SigV4A,
+				SigningName:           getSigningName(authScheme),
+				SigningRegionSet:      getSigningRegionSet(authScheme),
+				DisableDoubleEncoding: getDisableDoubleEncoding(authScheme),
+			}
+			result = append(result, AuthenticationScheme(&v4aScheme))
+		case None:
+			noneScheme := AuthenticationSchemeNone{}
+			result = append(result, AuthenticationScheme(&noneScheme))
+		default:
+			unsupportedSchemes = append(unsupportedSchemes, authScheme["name"].(string))
+			continue
+		}
+	}
+
+	if len(result) == 0 {
+		return nil, &UnSupportedAuthenticationSchemeSpecifiedError{
+			UnsupportedSchemes: unsupportedSchemes,
+		}
+	}
+
+	return result, nil
+}
+
+type disableDoubleEncoding struct{}
+
+// SetDisableDoubleEncoding sets or modifies the disable double encoding option
+// on the context.
+//
+// Scoped to stack values. Use github.com/aws/smithy-go/middleware#ClearStackValues
+// to clear all stack values.
+func SetDisableDoubleEncoding(ctx context.Context, value bool) context.Context {
+	return middleware.WithStackValue(ctx, disableDoubleEncoding{}, value)
+}
+
+// GetDisableDoubleEncoding retrieves the disable double encoding option
+// from the context.
+//
+// Scoped to stack values. Use github.com/aws/smithy-go/middleware#ClearStackValues
+// to clear all stack values.
+func GetDisableDoubleEncoding(ctx context.Context) (value bool, ok bool) {
+	value, ok = middleware.GetStackValue(ctx, disableDoubleEncoding{}).(bool)
+	return value, ok
+}
+
+func getSigningName(authScheme map[string]interface{}) *string {
+	signingName, ok := authScheme["signingName"].(string)
+	if !ok || signingName == "" {
+		return nil
+	}
+	return &signingName
+}
+
+func getSigningRegionSet(authScheme map[string]interface{}) []string {
+	untypedSigningRegionSet, ok := authScheme["signingRegionSet"].([]interface{})
+	if !ok {
+		return nil
+	}
+	signingRegionSet := []string{}
+	for _, item := range untypedSigningRegionSet {
+		signingRegionSet = append(signingRegionSet, item.(string))
+	}
+	return signingRegionSet
+}
+
+func getSigningRegion(authScheme map[string]interface{}) *string {
+	signingRegion, ok := authScheme["signingRegion"].(string)
+	if !ok || signingRegion == "" {
+		return nil
+	}
+	return &signingRegion
+}
+
+func getDisableDoubleEncoding(authScheme map[string]interface{}) *bool {
+	disableDoubleEncoding, ok := authScheme["disableDoubleEncoding"].(bool)
+	if !ok {
+		return nil
+	}
+	return &disableDoubleEncoding
+}