AggregationDataStore : RequestScope should include fields requested for a given entity load

[aklish]

The Aggregation Data Store needs to know what attributes and relationships are being fetched so that it can construct a complete JPQL query.

While this information is available today for JSON-API (via the request headers and the list of sparse fields for a given entity model), this capability does not exist for GraphQL.

Expected Behavior

A new field, requestedSubgraph will be set inside the requestScope each time loadObjects or getRelationship is called on the DataStoreTransaction.

This field will contains a nested map containing the entity relationship graph (entities, fields, and relationships to other entities) that is being requested starting at the current collection or entity that is being loaded.

Possible Solution

Both JSON-API and GraphQL will require changes:

1. JSON-API can construct this graph from the &include and &fields query parameters.
2. GraphQL can look at the SelectionSet passed in the DataFetchingEnvironment.

Context

#804

[QubitPi]

This issue is done by #896