Migrate from express-graphql to graphql-http

Same change as was just made in Mockttp.

Appears to be a much smaller package with exactly the same
functionality, officially supported by graphql org, and actively
maintained while the old one is now deprecated. No brainer.

Author: pimterry

package-lock.json

@@ -66,8 +66,8 @@
     "env-paths": "^1.0.0",
     "event-stream": "^4.0.1",
     "express": "^4.17.3",
-    "express-graphql": "^0.11.0",
     "graphql": "^15.8.0",
+    "graphql-http": "^1.22.0",
     "graphql-tag": "^2.12.6",
     "gunzip-maybe": "^1.4.2",
     "iconv-lite": "^0.4.24",

package.json

@@ -3,7 +3,7 @@ import type { Application as ExpressApp } from 'express';
 
 import { makeExecutableSchema } from '@graphql-tools/schema';
 import { GraphQLScalarType } from 'graphql';
-import { graphqlHTTP } from 'express-graphql';
+import { createHandler as createGraphQLHandler } from 'graphql-http/lib/use/express';
 import gql from 'graphql-tag';
 import { ApiModel } from './api-model';
 
@@ -170,8 +170,5 @@ export function exposeGraphQLAPI(
         resolvers: buildResolvers(apiModel)
     });
 
-    server.post('/', graphqlHTTP({
-        schema,
-        graphiql: false
-    }));
+    server.post('/', createGraphQLHandler({ schema }));
 }