Add an example using the DynamoDBMapper

[SalusaSecondus]

No description provided.

[david-koenig]

Successfully built and ran this test. Output:

Plaintext Record: DataPoJo [partitionAttribute=is this, sortAttribute=55, example=data, someNumbers=99, someBinary=[0, 1, 2], leaveMe=alone]
Encrypted Record: {amzn-ddb-map-desc={B: java.nio.HeapByteBuffer[pos=0 lim=760 cap=760],}, leave me={S: alone,}, partition_attribute={S: is this,}, and some binary={B: java.nio.HeapByteBuffer[pos=0 lim=32 cap=32],}, some numbers={B: java.nio.HeapByteBuffer[pos=0 lim=32 cap=32],}, sort_attribute={N: 55,}, amzn-ddb-map-sig={B: java.nio.HeapByteBuffer[pos=0 lim=32 cap=32],}, example={B: java.nio.HeapByteBuffer[pos=0 lim=32 cap=32],}}
Decrypted Record: DataPoJo [partitionAttribute=is this, sortAttribute=55, example=data, someNumbers=99, someBinary=[0, 1, 2], leaveMe=alone]