[AVRO] Incorrect JSON in AVRO schema gets only "Failed to register schema in registry" message

[murbanowicz]

First of all thank you for such an amazing piece of software.

We have small issue, which is not really breaking anything, but definitely makes it harder to catch errors quickly.

Incorrect JSON, particularly with trailing commas like this (after the id field definition) gives no clue on the CR description about the reason of failure.

{
    "type": "record",
    "name": "OrderCancelled",
    "fields": [
        {
            "name": "headers",
            "type": {
                "type": "record",
                "name": "Headers",
                "fields": [
                    {
                        "name": "id",
                        "type": "string"
                    }, // <<-- this comma
                ]
            }
        },
    ]
}

Would be nice to check JSON parsability before even trying to send it to Schema Registry and set the clear information if the JSON is not parsable.