[REST] JSON response for invoice is missing friendly_id param available in the XML response

<?xml version="1.0" encoding="UTF-8"?>
<invoice version="1.0">
  <id>682097609</id>
  <friendly_id>2018-02-00000001</friendly_id>
  <creation_type>manual</creation_type>
  <state>open</state>
  <paid_at></paid_at>
  <due_on></due_on>
  <issued_on></issued_on>
  <currency>USD</currency>
  <cost>0.0</cost>
  <cost_without_vat>0.0</cost_without_vat>
  <payment_transactions_count>0</payment_transactions_count>
</invoice>

{                                                                                                                                 
  "invoice": {                                                                                                                    
    "id": 682097624,                                                                                                              
    "created_at": "2018-02-19T10:30:50Z",                                                                                         
    "updated_at": "2018-02-19T10:30:50Z",                                                                                         
    "state": "open",                                                                                                              
    "currency": "USD",                                                                                                            
    "cost": 0,                                                                                                                    
    "vat_rate": null,                                                                                                             
    "vat_amount": 0,                                                                                                              
    "cost_without_vat": 0,                                                                                                        
    "period": {                                                                                                                   
      "begin": "2018-02-01",                                                                                                      
      "end": "2018-02-28"                                                                                                         
    },                                                                                                                            
    "creation_type": "manual"
 }                                                                                                                                                                                                             
}