GraphQL query fragments

[JacobMountain]

Currently interface selections are inlined, this can lead to overly verbose/complex queries. fragments can be used to reduce the size of the query.
e.g.

query Hero($episode: Episode) { 
    hero(episode: $episode) { 
        id 
        name 
        friends { 
            id 
            name 
            ... on Human { 
                homePlanet 
                height 
                mass 
                __typename 
            } 
            ... on Droid { 
                primaryFunction 
                __typename 
            } 
            __typename 
        } 
        appearsIn
        ... on Human { 
            homePlanet 
            height 
            mass
            appearsIn 
            starships { 
                id 
                name 
                length 
                coordinates 
                __typename 
            } 
            __typename 
        } 
        ...Droid { 
            appearsIn 
            primaryFunction 
            __typename 
        } 
        __typename 
    } 
}

could be reduced to

query Hero($episode: Episode) { 
    hero(episode: $episode) { 
        id 
        name 
        friends { 
            id 
            name 
            ...Human
            ...Droid
            __typename 
        } 
        appearsIn
        ... Human
        ... on Droid
        __typename 
    } 
}
fragment Human on Human {
    homePlanet 
    height 
    mass 
    __typename 
}
fragment Droid on Droid {
    appearsIn 
    primaryFunction 
    __typename
}

Although at the final depth it wouldn't be able to use the fragment as it would add unnecessary depth

[JacobMountain]

Need to figure out how we handle depth/max depth with fragments