As part of the Metainfo Refactoring, we need to make the Metainfo Loop
working with both the current PointerDB and the new Metabase. Thus, the
Metainfo Loop should pass to the Observer interface more specific Object
and Segment types instead of pb.Pointer.
After this change, there are still a couple of use cases that require
access to the pb.Pointer (hence we have it as a field in the
metainfo.Segment type):
1. Expired Deletion Service
2. Repair Service
It would require additional refactoring in these two services before we
are able to clean this.
Change-Id: Ib3eb6b7507ed89d5ba745ffbb6b37524ef10ed9f
Currently there is confusion between responsibilities of
metainfo.Endpoint, metainfo.Service, PointerDB.
By separating database "service" into a separate package and
its types allows to disentagle them.
This gives us responsibilities:
1. metainfo.Endpoint - translates requests and permissions
2. metainfo.Service - handles requests and coordinates with
objectdeletion, piecedeletion, metabase
3. metabase.Service - communication with the database interface and invariants
Currently metabase will contain the types necessary to coordinate
information.
Change-Id: If8c992b4b9d9e70a56bbd8a378a5af6b1a2ec34e
