Iceberg REST catalog should respond with 4xx code when namespace or table is not found

[rampage644]

Currently it returns internal cryptic error and 500 http code:

$ http localhost:3000/catalog/v1/51e0acba-e206-4720-9769-f2e029857554/namespaces/public_snowplow_manifest
HTTP/1.1 500 Internal Server Error
access-control-allow-origin: *
content-length: 84
content-type: text/plain; charset=utf-8
date: Mon, 03 Feb 2025 22:28:32 GMT
vary: origin, access-control-request-method, access-control-request-headers

Database not found: db.51e0acba-e206-4720-9769-f2e029857554.public_snowplow_manifest