Add subscription skeleton

This follows the first few steps in the [Apollo
Documentation](https://www.apollographql.com/docs/graphql-subscriptions/subscriptions-to-schema.html)
for adding subscriptions to graphql.  It sets up the schema to handle
subscriptions and also creates the very initial integration with the
PubSub implementation baked into the graphql-subscriptions library.

As noted in that library, it is only appropriate for demos, not
production.  We will eventually want to replace it with a more robust
PubSub implementation.

Issue #44
Issue #43

package.json

@@ -18,6 +18,7 @@
     "express": "^4.16.3",
     "express-graphql": "^0.6.12",
     "graphql": "^0.11.0 || ^0.12.0 || ^0.13.0 || ^14.0.0",
+    "graphql-subscriptions": "^1.0.0",
     "graphql-tag": "^2.10.0",
     "moment": "^2.24.0",
     "node-schedule": "^1.3.0",

src/server/schema/index.js

@@ -4,11 +4,13 @@ import { GraphQLSchema } from 'graphql'
 // App Imports
 import query from './query'
 import mutation from './mutation'
+import subscription from './subscription'
 
 // Schema
 const schema = new GraphQLSchema({
   query,
   mutation,
+  subscription,
 })
 
 export default schema

src/server/schema/sentences/fields/subscriptions.js

@@ -0,0 +1,13 @@
+import { PubSub } from 'graphql-subscriptions'
+
+// App Imports
+import SentenceType from '../type'
+
+const pubsub = new PubSub()
+
+const sentenceAdded = {
+  type: SentenceType,
+  resolve: () => pubsub.asyncIterator('sentenceAdded'),
+}
+
+export default sentenceAdded

src/server/schema/subscription.js

@@ -0,0 +1,16 @@
+import { GraphQLObjectType } from 'graphql'
+
+// App Imports
+import * as sentence from './sentences/fields/subscriptions'
+
+// Compile into a single export
+const subscription = new GraphQLObjectType({
+  name: 'subscription',
+  description: '...',
+
+  fields: {
+    ...sentence,
+  },
+})
+
+export default subscription

yarn.lock

@@ -3624,6 +3624,13 @@ graphql-anywhere@^4.1.0-alpha.0:
     apollo-utilities "^1.1.3"
     tslib "^1.9.3"
 
+graphql-subscriptions@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/graphql-subscriptions/-/graphql-subscriptions-1.0.0.tgz#475267694b3bd465af6477dbab4263a3f62702b8"
+  integrity sha512-+ytmryoHF1LVf58NKEaNPRUzYyXplm120ntxfPcgOBC7TnK7Tv/4VRHeh4FAR9iL+O1bqhZs4nkibxQ+OA5cDQ==
+  dependencies:
+    iterall "^1.2.1"
+
 graphql-tag@^2.10.0, graphql-tag@^2.4.2:
   version "2.10.1"
   resolved "https://registry.yarnpkg.com/graphql-tag/-/graphql-tag-2.10.1.tgz#10aa41f1cd8fae5373eaf11f1f67260a3cad5e02"
@@ -4367,7 +4374,7 @@ isstream@~0.1.2:
   resolved "https://registry.yarnpkg.com/isstream/-/isstream-0.1.2.tgz#47e63f7af55afa6f92e1500e690eb8b8529c099a"
   integrity sha1-R+Y/evVa+m+S4VAOaQ64uFKcCZo=
 
-iterall@^1.2.2:
+iterall@^1.2.1, iterall@^1.2.2:
   version "1.2.2"
   resolved "https://registry.yarnpkg.com/iterall/-/iterall-1.2.2.tgz#92d70deb8028e0c39ff3164fdbf4d8b088130cd7"
   integrity sha512-yynBb1g+RFUPY64fTrFv7nsjRrENBQJaX2UL+2Szc9REFrSNm1rpSXHGzhmAy7a9uv3vlvgBlXnf9RqmPH1/DA==