[Server v3] Remove code duplication for each authenticated route

[vxgmichel]

Those blocks are repeated for each authenticated route:

        match await self.organization._get(conn, organization_id):
            case OrganizationGetBadOutcome.ORGANIZATION_NOT_FOUND:
                return RealmShareStoreBadOutcome.ORGANIZATION_NOT_FOUND
            case Organization() as org:
                pass

        if org.is_expired:
            return RealmShareStoreBadOutcome.ORGANIZATION_EXPIRED

        match await self.user._check_device(conn, organization_id, author):
            case CheckDeviceBadOutcome.DEVICE_NOT_FOUND:
                return RealmShareStoreBadOutcome.AUTHOR_NOT_FOUND
            case CheckDeviceBadOutcome.USER_NOT_FOUND:
                return RealmShareStoreBadOutcome.AUTHOR_NOT_FOUND
            case CheckDeviceBadOutcome.USER_REVOKED:
                return RealmShareStoreBadOutcome.AUTHOR_REVOKED
            case (UserProfile(), DateTime()):
                pass

That's a lot of duplication that can be factorized away.