vendor: update buildkit to master@31c870e82a48

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/aws/aws-sdk-go-v2/credentials/processcreds/provider.go

@@ -149,12 +149,24 @@ func NewProviderCommand(builder NewCommandBuilder, options ...func(*Options)) *P
 	return p
 }
 
-type credentialProcessResponse struct {
-	Version         int
-	AccessKeyID     string `json:"AccessKeyId"`
+// A CredentialProcessResponse is the AWS credentials format that must be
+// returned when executing an external credential_process.
+type CredentialProcessResponse struct {
+	// As of this writing, the Version key must be set to 1. This might
+	// increment over time as the structure evolves.
+	Version int
+
+	// The access key ID that identifies the temporary security credentials.
+	AccessKeyID string `json:"AccessKeyId"`
+
+	// The secret access key that can be used to sign requests.
 	SecretAccessKey string
-	SessionToken    string
-	Expiration      *time.Time
+
+	// The token that users must pass to the service API to use the temporary credentials.
+	SessionToken string
+
+	// The date on which the current credentials expire.
+	Expiration *time.Time
 }
 
 // Retrieve executes the credential process command and returns the
@@ -166,7 +178,7 @@ func (p *Provider) Retrieve(ctx context.Context) (aws.Credentials, error) {
 	}
 
 	// Serialize and validate response
-	resp := &credentialProcessResponse{}
+	resp := &CredentialProcessResponse{}
 	if err = json.Unmarshal(out, resp); err != nil {
 		return aws.Credentials{Source: ProviderName}, &ProviderError{
 			Err: fmt.Errorf("parse failed of process output: %s, error: %w", out, err),