[Server] Some performance improvements

src/api/endpoints/aggregation/users/followers.js

@@ -25,6 +25,10 @@ module.exports = (params) =>
 	// Lookup user
 	const user = await User.findOne({
 		_id: new mongo.ObjectID(userId)
+	}, {
+		fields: {
+			_id: true
+		}
 	});
 
 	if (user === null) {

src/api/endpoints/aggregation/users/following.js

@@ -25,6 +25,10 @@ module.exports = (params) =>
 	// Lookup user
 	const user = await User.findOne({
 		_id: new mongo.ObjectID(userId)
+	}, {
+		fields: {
+			_id: true
+		}
 	});
 
 	if (user === null) {

src/api/endpoints/aggregation/users/like.js

@@ -25,6 +25,10 @@ module.exports = (params) =>
 	// Lookup user
 	const user = await User.findOne({
 		_id: new mongo.ObjectID(userId)
+	}, {
+		fields: {
+			_id: true
+		}
 	});
 
 	if (user === null) {

src/api/endpoints/aggregation/users/post.js

@@ -25,6 +25,10 @@ module.exports = (params) =>
 	// Lookup user
 	const user = await User.findOne({
 		_id: new mongo.ObjectID(userId)
+	}, {
+		fields: {
+			_id: true
+		}
 	});
 
 	if (user === null) {