Add a warning if JceNameLocalDelegatedKey is created with dangerously short keys

[mattsb42-aws]

In order to maintain compatibility with the Java client, we must allow any valid key size for JceNameLocalDelegatedKey. However, some key sizes are known to be dangerously small. We cannot block small keys, but we should raise a warning if they are used.

[mattsb42-aws]

For reference, the best place to implement this will be in the load_key methods in JAVA_ENCRYPTION_ALGORITHM and JAVA_AUTHENTICATOR member classes.

https://github.com/awslabs/aws-dynamodb-encryption-python/blob/master/src/dynamodb_encryption_sdk/internal/crypto/jce_bridge/primitives.py#L559-L563

https://github.com/awslabs/aws-dynamodb-encryption-python/blob/master/src/dynamodb_encryption_sdk/internal/crypto/jce_bridge/authentication.py#L317-L326

[mattsb42-aws]

TBD: For the following algorithms we need to determine the minimum key size for which we will not warn.

• AES
• RSA
• HMAC

[mattsb42-aws]

Key sizes that we will warn on are:

• AES : none
• RSA : less than 2048
• HMAC : less than 128