Is your enhancement request related to a problem? Please describe.
SchemaRegistryService is hardcoded to use SchemaRegistryServiceImpl in org.apache.pulsar.broker.service.schema.SchemaRegistryService#create

this is required because we want to use custom schema store with custom compatibility checks.

Describe the solution you'd like
broker.conf will have a new config called schemaRegistryClassName which will have the name of the class to be used