Handling compression on responses?

[tylanderson]

Currently stac-server doesn't compress responses emitted from the api lambda, which can lead to responses erroring due to lambda's 6MB response size limit.

Taking a look at #271, it looks like compression was previously removed when pre- and post- hooks were added (I assume to simplify pre- and post-hooks).

Some additional logic in the post-hook handler would allow handling compressed responses