Include extension in S3 key (#1426)

api/resolvers/upload.js

@@ -49,7 +49,10 @@ export default {
       }
 
       const upload = await models.upload.create({ data: { ...fileParams } })
-      return createPresignedPost({ key: String(upload.id), type, size })
+
+      const extension = type.split('/')[1]
+      const key = `${upload.id}.${extension}`
+      return createPresignedPost({ key, type, size })
     }
   }
 }