Support partial return values from denormalize()

[jonaskello]

Today the denormalize function only returns a result if the whole query could be resolved from cache. It would be nice it it could return as much as possible, and also return an updated version of the query with the available fields removed. That query could be used to fill the missing parts of the cache. This would work best with data that is read-only because otherwise you might get inconsistent data in cache unless you refetch the full query.

[jonaskello]

Instead of returning partial as a boolean we could return the diffed query. This could be implemented today by always returning the full query and no result if something is missing.

[jonaskello]

Perhaps returning partial should be optional for performance reasons. Bailing out early when data is missing will be quicker. Something like this could be used:

const denormResult = denormalize(query, variables, normMap, partial);

Where the partial parameter is a boolean specifying if partial results should be returned. The return value could include a similar partial flag to indicate if the result is partial.

export interface DenormalizationResult {
  readonly data: RootFields | undefined;
  readonly fields: FieldsMap;
  readonly partial: boolean;
}

However if the result should include the remaining query then perhaps that is enough:

export interface DenormalizationResult {
  readonly data: RootFields | undefined;
  readonly fields: FieldsMap;
  readonly remaining: GraphQL.Document | undefined;
}