Confluent Schema Registry supports tags, metadata, and rules, which together support the concept of a [Data Contract](https://docs.confluent.io/platform/7.9/schema-registry/fundamentals/data-contracts.html).

This change adds support only for [metadata properties](https://docs.confluent.io/platform/7.9/schema-registry/fundamentals/data-contracts.html#metadata-properties) that may include arbitrary information about the schema, such as who created it:

```json
{
  "schema": "...",
  "metadata": {
    "properties": {
      "owner": "Bob Jones",
      "email": "[email protected]"
    }
  }
}
```

Properties may also include [major schema version](https://docs.confluent.io/platform/7.9/schema-registry/fundamentals/data-contracts.html#application-major-versioning) to highlight incompatible changes throughout the schema history:

```json
{
  "schema": "...",
  "metadata": {
    "properties": {
      "application.major.version": "2"
    }
  }
}
```