tolerant parsing of OAF-store-graph mdstores #180

This PR introduces a change in the serialisation of the records stored in the OAF-store-graph mdstores. They were stored in Kryo (binary) format, therefore any slight change in the schema version would made them unreadable, forcing us to recreate them quite frequently. Instead, we're going to store them in as a json serialization, so that reading them again in the graph construction phase with a parser (com.fasterxml.jackson.databind.ObjectMapper) we have better changes to support backward compatible changes in the evolution of the schema.

val mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)

This PR introduces a change in the serialisation of the records stored in the `OAF-store-graph` mdstores. They were stored in Kryo (binary) format, therefore any slight change in the schema version would made them unreadable, forcing us to recreate them quite frequently. Instead, we're going to store them in as a json serialization, so that reading them again in the graph construction phase with a parser (`com.fasterxml.jackson.databind.ObjectMapper`) we have better changes to support backward compatible changes in the evolution of the schema. ``` val mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) ```

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tolerant parsing of OAF-store-graph mdstores #180

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