Sum up invoice items for invoice-details

[allmightyspiff]

Invoice Top Level item should at least be the sum of itself and its children.
That top entry should not be 0.00$ (should be 60.57$)

 3097434296                       Server                                     Dual Intel Xeon Silver 4110 (16 Cores, 2.10 GHz) (ocp-master-3.chechu.me)                 $0.00    $0.00   2024-12-04    fra02
    >>>                      Second Processor                                               Intel Xeon Silver 4110 (16 Cores, 2.10 GHz)                                $0.00    $0.00       ---        --- 
    >>>                      Operating System                                                           No Operating System                                            $0.00    $0.00       ---        ---
    >>>                      Disk Controller                                                                   RAID 1                                                  $0.00   $60.57       ---        ---
    >>>                      First Hard Drive                                                          960GB SSD SED (5DWPD)                                           $0.00    $0.00       ---        ---
    >>>                      Public Bandwidth                                                         0 GB Bandwidth Allotment                                         $0.00    $0.00       ---        ---
    >>>                     Uplink Port Speeds                                                1 Gbps Redundant Private Network Uplinks                                 $0.00    $0.00       ---        ---
    >>>                    Public Network Port                                                          0 Mbps Public Uplink                                           $0.00    $0.00       ---        ---
    >>>                    Primary IP Addresses                                                             1 IP Address                                               $0.00    $0.00       ---        ---
    >>>                     Second Hard Drive                                                            960GB SSD (3 DWPD)                                            $0.00    $0.00       ---        ---
    >>>                      Third Hard Drive                                                            3.2TB NVMe SSD U.2                                            $0.00    $0.00       ---        ---
    >>>                     Fourth Hard Drive                                                            3.2TB NVMe SSD U.2                                            $0.00    $0.00       ---        --- 
    >>>                            RAM                                                                       128 GB RAM                                                $0.00    $0.00       ---        ---

see also https://github.ibm.com/SoftLayer/softlayer-cli/issues/884