Implement aliasing for fields

[krisgrint]

Relates to #11 and the discussion in PR #22

Aliasing of fields in forwarded queries does not appear to be supported out of the box.

Consider the following addition to the test cases in test/proxy.test.js. The first test cases passes, but the second two fail:

{
    name: 'should federate a basic service with queries with aliases on fields',
    services: [
      {
        schema: dedent`
        type Query {
          me: User
        }
        type User {
          id: ID!
          name: String!
          address: String
        }
      `,
        resolvers: {
          Query: {
            me: () => db.users[1]
          },
          User: {
            address: () => 'Banbury'
          }
        }
      }
    ],
    queries: [
      {
        query: '{ me { userId: id, name } }',
        expected: {
          me: {
            userId: '1', // returns the correct aliased field
            name: 'Jimmy'
          }
        }
      },
      {
        query: '{ me { id, firstName: name } }',
        expected: {
          me: {
            userId: '1',
            firstName: 'Jimmy' // returns null for entire me object
          }
        }
      },
      {
        query: '{ me { id, location: address } }',
        expected: {
          me: {
            id: '1',
            location: 'Banbury' // returns null for location
          }
        }
      }
    ]
  }

[Mazuh]

@krisgrint is this still needed or should be already closed after your PR have been merged? is there some work left to be done here that I can help?

[krisgrint]

@krisgrint is this still needed or should be already closed after your PR have been merged? is there some work left to be done here that I can help?

Hi @Mazuh no this issue is still to be done - aliasing of the query works, but aliasing of the fields still needs to be implemented.

[Mazuh]

I unassigned myself on this, because I don't have a good time window for it right now. So it is not a WIP.