Implement Harvester

According to https://app.diagrams.net/#G1L8WXp2Ldp1kAqYZMDZWjs0r_g8UzB3hX and https://docs.google.com/document/d/1EWL3C0FrHqoJMMK1_1XisLBOokpPUpbwSaKteQrcYo0/edit#

the harvester should be capable of

• listening on a queue for new harvesting jobs
• querying the configured backend with static/dynamic parameters
• resolve items to be pushed to a configurable queue (registration, preprocessing, deletion, ...)

Endpoints include:

• resolving hierarchies of STAC-Catalogues
• OpenSearch
• STAC API
• OGC API Records