Handle Device ID with Push Notification Token

[zdmc23]

As of DiscipleTools/disciple-tools-mobile-app#179, we are sending another field: add_device_id when submitting the Push Notification Token to the D.T API:

https://${domain}/wp-json/dt/v1/user/update

{
  "add_push_token": "ExponentPushToken[xxxxxxxxxxxxxxxxxxxxxx]",
  "add_device_id": "Apple:iPhone XR:2018:iOS:13.3.1"
}

So we will want to decide how to best handle this on the D.T API side. We could use the Device ID as a key to a hashmap and store only the latest token for a given device:

$myhashmap = array();
$myhashmap[$fields["add_device_id"]] = $fields["add_push_token"];

[zdmc23]

New JSON format:

{
    add_push_token: {
        token: expoPushToken,
        device_id: uniqueId
    },
},

Related mobile app commit: DiscipleTools/disciple-tools-mobile-app@0a11975