Add @koa/json-filter, allowing user to limit the fields being returned

This doesn't reduce the query, and should play nicely with cache. All it
does is remove any fields that aren't explicitly asked for, using the
`filter` query.

Author: jhpratt

package-lock.json

@@ -32,6 +32,7 @@
   },
   "homepage": "https://github.com/r-spacex/SpaceX-API",
   "dependencies": {
+    "@koa/json-filter": "^1.0.0",
     "cheerio": "^1.0.0-rc.2",
     "fuzzball": "^1.1.5",
     "koa": "^2.5.3",

package.json

@@ -4,6 +4,7 @@ const cache = require('koa-redis-cache');
 const compress = require('koa-compress');
 const cors = require('koa2-cors');
 const helmet = require('koa-helmet');
+const jsonFilter = require('@koa/json-filter');
 const Koa = require('koa');
 const logger = require('koa-morgan');
 const MongoClient = require('mongodb');
@@ -95,6 +96,9 @@ if (process.env.NODE_ENV === 'production') {
   app.use(cache(options));
 }
 
+// Allow user to restrict the keys returned
+app.use(jsonFilter());
+
 // Allow pretty print via pretty=true querystring
 // Pretty printed json will NOT be cached
 app.use(json({ pretty: false, param: { pretty: true } }));