Add support for JSON Schema while producing a message

[txs4444]

Current behavior:

When producing message to topic and as a schema JSON Schema is chosen then exception is thrown because AvroSerializer is used regardless of schema type.

org.apache.avro.AvroRuntimeException: Not a record schema: null
	at org.apache.avro.generic.GenericData$Record.<init>(GenericData.java:215)
	at org.akhq.utils.AvroSerializer.recordSerializer(AvroSerializer.java:55)
	at org.akhq.modules.AvroSerializer.fromJsonToAvro(AvroSerializer.java:73)
	at org.akhq.modules.AvroSerializer.toAvro(AvroSerializer.java:60)
	at org.akhq.repositories.RecordRepository.produce(RecordRepository.java:612)
	at org.akhq.repositories.RecordRepository.produce(RecordRepository.java:493)
	at org.akhq.controllers.TopicController.produce(TopicController.java:142)
	at org.akhq.controllers.$TopicControllerDefinition$$exec4.invokeInternal(Unknown Source)
	at io.micronaut.context.AbstractExecutableMethod.invoke(AbstractExecutableMethod.java:151)
	at io.micronaut.context.DefaultBeanContext$4.invoke(DefaultBeanContext.java:482)
	at io.micronaut.web.router.AbstractRouteMatch.execute(AbstractRouteMatch.java:303)
	at io.micronaut.web.router.RouteMatch.execute(RouteMatch.java:121)
	at io.micronaut.http.server.netty.RoutingInBoundHandler.emitRouteResponse(RoutingInBoundHandler.java:1533)
	at io.micronaut.http.server.netty.RoutingInBoundHandler.access$2100(RoutingInBoundHandler.java:151)
	at io.micronaut.http.server.netty.RoutingInBoundHandler$6$1.request(RoutingInBoundHandler.java:1500)
	at io.reactivex.internal.subscriptions.SubscriptionHelper.deferredSetOnce(SubscriptionHelper.java:202)
	at io.reactivex.internal.operators.single.SingleFlatMapPublisher$SingleFlatMapPublisherObserver.onSubscribe(SingleFlatMapPublisher.java:107)
	at io.micronaut.http.server.netty.RoutingInBoundHandler$6.doSubscribe(RoutingInBoundHandler.java:1488)
	at io.micronaut.http.server.netty.RoutingInBoundHandler$6.lambda$subscribe$0(RoutingInBoundHandler.java:1482)
	at io.micrometer.core.instrument.composite.CompositeTimer.record(CompositeTimer.java:79)
	at io.micrometer.core.instrument.Timer.lambda$wrap$0(Timer.java:157)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)

Proposed solution:
#919

[txs4444]

The proposed solution was merged - closing the issue.