Please suport Schema References

Nobody has claimed this yet.

Confluent Platform 5.5.0 support [Schema References](https://docs.confluent.io/current/schema-registry/serdes-develop/index.html#schema-references), the ability of a schema to refer to other schemas.

[Here's](https://www.confluent.io/blog/multiple-event-types-in-the-same-kafka-topic/) a blog post that goes a bit into detail.

The schema you want to register contains a reference:

```json
{
"namespace": "my.little.schema",
"name": "Test",
"type": "record",
"fields": [
{
"name": "name",
"type": {
"name": "Name",
"type": "some.other.schema" <====
}
}
]
}
```
The json you sent to the SR contains a `references` section, listing all referenced schemas with versions:

```json
{
"schema": "...",
"references": [
{
"name": "some.other.schema",
"subject": "name",
"version": 42
}
]
}
```

Start by locating the schema registration request path and its existing request serialization, then compare it with the linked Confluent Schema References documentation. Done means registration requests can represent and send the listed references, including their names, subjects, and versions, with tests covering the new request shape.

Written by the indexing model from the issue text.