Nullable fields in a body to be configurable

[luica13]

For viewing message body in AvroToJsonSerializer it was added to show only non_null and non_empty fields. It will be better to have it configurable, as these fields needed to be viewed for many cases(check wether nullable fields are pushed, etc.)

0.17.0...0.18.0#diff-e52f62409aed8a22b8fe718f08bb367e172a445c078a145b771dd3c302d0aed8R17

[tchiotludo]

Simple here !
a PR is welcome to add some configuration properties for that

[magnusgundersen]

Did a quick suggestion on solving this feature. #799
Any thoughs?

[twobeeb]

I just encountered this issue recently.

It was very difficult to understand at first because the field defined with AVRO was mandatory yet it was not displayed in AKHQ.
After investigation, the producer set the value "" which doesn't show up in AKHQ in 0.18.

Message displayed with kafka-avro-console-consumer :

{
  "ProductionDay": 1631671200000,
  "Machine": "", <----- Mandatory in AVRO
  "Series": null,  <----- Optional in AVRO
  "Operator": {
    "string": "xxxxx"
  },
  "Product": {
    "SerialNumber": "0014479"
  }
}

The same message in AKHQ :

{
  "ProductionDay": 1631671200000,
  "Operator": {
    "string": "xxxxx"
  },
  "Product": {
    "SerialNumber": "0014479"
  }
}

I believe the defaults NON_EMPTY and NON_NULL are VERY misleading (NON_EMPTY particularly)
@tchiotludo @magnusgundersen
What's your opinion on this (the defaults set on PR #799) ?

[tchiotludo]

good catch, I remove the NON_EMPTY defaults