[Avro] schema (multiple record, null default of record) & convertor

### first type is null

  {
     "name":"my_optional_date",
     "type":[ "null", {"type" : "long", "logicalType": "timestamp-millis"}], "default": null
  }

https://stackoverflow.com/questions/45581437/how-to-specify-converter-for-default-value-in-avro-union-logical-type-fields

How to specify converter for default value in Avro Union logical type fields?

{
    "type": "record",
    "name": "OrderBook",
    "namespace": "my.types",
    "doc": "Test order update",
    "fields": [
        {
            "name": "bids",
            "type": {
                "type": "array",
                "items": {
                    "type": "record",
                    "name": "OrderBookVolume",
                    "namespace": "my.types.bid",
                    "fields": [
                        {
                            "name": "price",
                            "type": "double"
                        },
                        {
                            "name": "volume",
                            "type": "double"
                        }
                    ]
                }
            }
        },
        {
            "name": "asks",
            "type": {
                "type": "array",
                "items": "my.types.bid.OrderBookVolume"
            }
        }
    ]
}

https://stackoverflow.com/questions/48100575/avro-multiple-record-of-same-type-in-single-schema

Avro multiple record of same type in single schema

https://toolslick.com/generation/metadata/avro-schema-from-json

Avro Schema From JSON Generator - Tool Slick