Endpoint with schema’s raw JSON

[rkluszczynski]

Hello,
when using schema-registry in version 3.0.0, there is no method to get schema as valid JSON in response body. For example this is needed for Hive integration with schema-registry. This could be accomplished in two ways.

First would use query parameter to force JSON response.

GET /subjects/(string: subject)/versions/(versionId: version)?format=json

Second would be additional endpoint which should just output JSON.

GET /subjects/(string: subject)/versions/(versionId: version)/raw

I think, possible errors should be handled the same way like by endpoint:
GET /subjects/(string: subject)/versions/(versionId: version).

What do you think, is it possible to add such endpoint to schema-registry?
We are eager prepare the pull request:)

Kind regards,
Rafal Kluszczynski

[rayokota]

Fixed by #876