REST post plugin broken from Drupal 8.4.5 to 8.5 I just upgraded my Drupal installation from 8.4.5 to 8.5
Now my REST plugin is not getting any data on POST.

My client post like this:

POST /rgptemprest?_format=hal_json HTTP/1.1
Host: 10.10.10.1:443
Authorization: Basic ****REPLACED******
Content-Type: application/hal+json
Accept: application/hal+json
User-Agent: ESP8266
Connection: close
Content-Length: 108

{"netcard":"997800940160","DS18B20":"28ADBCE70800008C","battery":"2952","temperature":"23.375","rssi":"-33"}


On my drupal server I have a plugin
with this code (not complete)

public function post(array $data = []) 
{
    var_dump($data);
    if (!empty($data))
    {


....

And here I see the difference 
on 8.4.5 it show an array of the data sent:

array(5) {
  ["netcard"]=&gt;
  string(12) "997800940160"
  ["DS18B20"]=&gt;
  string(16) "28ADBCE70800008C"
  ["battery"]=&gt;
  string(4) "2952"
  ["temperature"]=&gt;
  string(6) "23.500"
  ["rssi"]=&gt;
  string(3) "-33"
}


but on 8.5 it's empty

array(0) {
}


What has changed between 8.4.5 and 8.5? And what do I need to change?
Wim Leers found the answer:

Change this:

public function post(array $data = []) 


to:

public function post(array $data)