Metod: POST URL: https://fcm.googleapis.com/fcm/send
Body:
{
"to" : "Token del cliente",
"notification" : {
"body" : "Body of Your Notification",
"title": "Title of Your Notification"
},
"data" : {
"body" : "Body of Your Notification in Data",
"title": "Title of Your Notification in Title",
"key_1" : "Value for key_1",
"key_2" : "Value for key_2"
}
}