Features/1.10 ready

[rkorzeniec]

This PR should (tested on the main app) make the graphql-preload gem ready for the new AST interpreter.

Changes in this PR are heavily based on ConsultingMD#25, with few minor changes, by making it more modular and properly using the options hash for field extensions.

The branch on the main app is updates/graphql-1.10.
The page I tested the preloading on http://localhost:3001/en-ch/explore/womens
You can compare using the original gem (or pointing to master) of this fork and pointing to this branch. The amount of DB calls and N+1s drops severely.

P.S. - also one day we might be forced to do this one too... ConsultingMD#32

[rkorzeniec]

@severin I'd need help adding this project to codeship, no permissions for that again 😉 while at it, any chance you could add the graphql-result_cache gem also, I'd like to set it up there too.

[severin]

@rkorzeniec I tested the following combinations:

• main app master branch: 24s for the query, thereof 90ms database time, no N+1 queries in the logs ✅
• main app updates/graphql-1.10 branch using this repo's master: 29s for the query, thereof 3+s database time, lots of N+1 queries ⛔
• main app updates/graphql-1.10 branch using this PR's branch: 22s for the query, 90ms database time, no N+1 queries ✅

I quickly skimmed the code but did not thoroughly review it. If you wish me to do that please rerequest review.