Interfaced relations fix

[ChristiaanScheermeijer]

Hi,

This is my first PR to this repository. The code is quite complex so I can't oversee all edge cases regarding these changes.

This PR will fix relation mutations with interfaced types. Given the following schema:

interface Person {
  userId: ID!
  name: String
}

type User implements Person {
  userId: ID!
  name: String
}

type Actor implements Person {
  userId: ID!
  name: String
  awards: Int
}

type Movie {
  movieId: ID!
  actors: [Actor] @relation(name: "ACTORS", direction: "OUT")
  seenBy: Person @relation(name: "SEEN_BY", direction: "OUT")
}

The following query will work:

mutation {
  AddMovieSeenBy(
    from: { movieId: "123" },
    to: { userId: "456" }
  ) {
    from {
      movieId
    }
    to {
      name
      ... on Actor {
        awards
      }
    }
  }
}

Happy to hear your feedback!

Fixed #182

[codecov-io]

Codecov Report

Merging #374 into master will increase coverage by 0.24%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
+ Coverage    96.3%   96.55%   +0.24%     
==========================================
  Files          24       24              
  Lines        2844     2846       +2     
==========================================
+ Hits         2739     2748       +9     
+ Misses        105       98       -7

Impacted Files	Coverage Δ
src/translate.js	98.68% <100%> (+0.36%)	⬆️
src/utils.js	94.51% <0%> (+0.95%)	⬆️

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[ChristiaanScheermeijer]

I'm not sure if this should be in this pull request, but the example server didn't work for on the master branch.

[johnymontana]

This is a result of upgrading the version of neo4j-driver, which removes the v1 namespace. I was lazy and only updated movies-middleware.js which is why this one was failing. My fault.

[johnymontana]

Looks good. Thanks @ChristiaanScheermeijer!