core/db: Special-case handling id=0 as the root folder.
core/db: Special-case handling id=0 as the root folder.

The purpose of doing this is being able to handle marking super groups as read within the Fever API.

It's technically possible that 0 gets assigned as the SERIAL-generated ID for an actual folder, but this is extraordinarily unlikely and avoids the need for implementing a stateful protocol on the server to correctly handle the "before" field.

jrupac/goliath,jrupac/goliath,jrupac/goliath,jrupac/goliath,jrupac/goliath