Drop support for pre- and post-hooks #918
Description
stac-server currently can be configured with user-provided pre- and post- hooks for managing tasks like A&E, filtering or enriching results returned, etc
These are tasks that also can be managed by a proxy such as https://github.com/developmentseed/stac-auth-proxy (and maybe more often are managed by a proxy in the wild) or in basic cases handled by ENABLE_COLLECTIONS_AUTHX
Relates to #916, as extra handling has to occur in the post-hook for compression etc