[FEATURE] Confluent Compatible REST Schema Registry API

[tspannhw]

Is your feature request related to a problem? Please describe.
Confluent and Cloudera, and others have a REST API in a format integrated in several OTS apps.

Describe the solution you'd like
Add a second REST API that follows their paradigms.

Cloudera and others have Confluent-compatible schema registries. It allows for easy replacement of Apache Kafka with Apache Pulsar. It would be useful for KoP.

https://docs.cloudera.com/csp/2.0.1/schema-registry-overview/topics/csp-schema_registry_component_architecture.html

https://docs.confluent.io/platform/current/schema-registry/develop/api.html

See:

https://github.com/riferrei/is-using-kop-a-good-idea/blob/cbc17d122b217c69696350c19fe91425506916df/stream-processing/docker-compose.yml

https://redpanda.com/blog/schema-registry

[eolivelli]

This is already implemented in KOP

[eolivelli]

There are a couple of changes that I haven't ported from DataStax fork (Starlight for Kafka) about allowing TLS.
But I can port them.

The KOP SchemaRegistry works well with all the known tools/IDEs and also supports multi-tenancy.

Data is stored on Pulsar topics