Should we support list_append in update expression?

[4ossiblellc]

We currently do not support list_append. We may need to consider that.

[4ossiblellc]

My plan is to have an option object as the third argument. Client should decide any new array value should be appended to or replaced from the original array.

[snolangps]

@4ossiblellc is this to extend on the ExpressionAttributeValues option?