Automatic dynamic type conversion

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## Background

We have a very specific use case where the data is in a CSV file and there is a separate file which stores avro schema.
We will have to convert the csv data into OCF format and send it out.

The problem we face is the CSV data is array of strings, and because of this the `BinaryFromNative` function returns type errors like

```
value does not match its schema: long: expected: Go numeric; received: string
```

### Schema

```avsc
{
"type": "record",
"name": "example",
"fields": [
{
"name": "customer",
"type": "long",
"default": 0
}
]
}
```

### Data

```go
map[string]interface{}{
"customer": "12323423",
}
```

## Feature request

1. Can we auto parse string to a type required by the avro schema at run time?
2. Also if a data is not present(empty string) default value must be populated

Start by reading the BinaryFromNative implementation and the schema-validation path that produces the reported type error. Clarify how runtime conversion should cover CSV strings and how empty strings interact with Avro defaults. Done means schema-compatible encoding for the requested conversions and default population, with tests for the long example and empty input.

Written by the indexing model from the issue text.