reduceGraph action helps to add to store data from a graph response.
Imagine a backend returns the next nested shape of user (like GraphQL does):
There is a selector that fetches this data from the store like that: a user with its company and the address of the company.
Then the store can be updated by dispatching the
ngrxEntityRelationshipReducer will catch this action, parse the data and put it into the store like that: