S3 listObjects is iterating through whole bucket

[graffzon]

Hello, thank you for your library!

We're using it to publish sites to S3 with different prefixes.
So we wanted to fine-tune our permissions on the S3 level to isolate those different websites (they are published from different microservices' builds) and came across this comment:

s3_website/src/main/scala/s3/website/S3.scala

Line 135 in 1636ce1

* We could filter the keys by prefix already on S3, but unfortunately s3_website test infrastructure does not currently support testing of that.

which hinders us from making the permissions to be isolated.
Also, I would assume that reading all the files could cause performance issues in case of a huge amount of them.

Do you maybe have some plans for improving it?