UDP Probe add expected payload

[momoXD007]

To my understanding UDP-probes do not offer the option to define an expected answer. Meaning a string or byte-sequence the probed endpoint should return if it is healthy.

Looking at the code it seems like the content of the answers received is parsed but simply not used at all later on, it could be interpreted in the following way (pseudo-code)

if  expected_payload != none 
{
     if msg == expected_payload
    {
         probe_sucess = true
   } else {
       probe_sucess = false
  }
}

[manugarg]

We can implement this through validators:
https://cloudprober.org/how-to/validators/