Mongodb Aggregation Problem
this is my user collection
{
"_id" : ObjectId("58e8cb640f861e6c40627a06"),
"actorId" : "665991",
"login" : "petroav",
"gravatar_id" : "",
"url" : "https://api.github.com/users/petroav",
"avatar_url" : "https://avatars.gi...