fix(topic-data): add basic deserialization of avro primitive (tchiotludo#715)

close tchiotludo#700

Author: raphaelauv

src/main/java/org/akhq/models/Record.java

@@ -123,7 +123,14 @@ private String convertToString(byte[] payload, Integer schemaId, boolean isKey)
             return null;
         } else if (schemaId != null) {
             try {
-                GenericRecord record = (GenericRecord) kafkaAvroDeserializer.deserialize(topic, payload);
+                Object toType = kafkaAvroDeserializer.deserialize(topic, payload);
+                
+                //for primitive avro type
+                if (!(toType instanceof GenericRecord)){
+                    return String.valueOf(toType);
+                }
+
+                GenericRecord record = (GenericRecord) toType;
                 return AvroToJsonSerializer.toJson(record);
             } catch (Exception exception) {
                 this.exceptions.add(exception.getMessage());