[Feature] Add validations at a consumer level

[koushikr]

Right now, the schema validations are basis the class definition, derived at the app startup. While this will help validate the data types at a production level, the ask is to also have a consumption level validation.

To validate at a consumer level, it is required to inspect all payloads that come your way - has to be implemented for JSON, AVRO and PROTOBUF - and at a message level. It is CPU intensive. So may need to think of sampling requests - at the cost of accuracy. Could be various strategies as well.