Support AWS KMS grant tokens

[seebees]

There is no simple support for AWS KMS grant tokens.
Customers can extend DirectKmsMaterialProvider
and override the generateDataKey or the appropriate AWS KMS call.

see

aws-dynamodb-encryption-java/sdk1/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/encryption/providers/DirectKmsMaterialProvider.java

Line 250 in 41ad9bf

protected GenerateDataKeyResult generateDataKey(final GenerateDataKeyRequest request,