common/service: Add lookup_object function
Add an utility function for looking up an object in the archive by its type and id. Supported object types are: content, directory, release, revision and snapshot.
Its purpose is to factorize some code that will be needed in the upcoming swh badge endpoints implementation. Notably, it enables to check that an object exists in the archive in order to return adequate HTTP status code.
Related to #2090 (closed)
Test Plan
Nex tests have been added.
Migrated from D2309 (view on Phabricator)