Update usermodel and gitignore

Route user objects created to user collections in Question-User-DB and add .env file to gitignore

Author: qiaoen17

Backend/.gitignore

@@ -1,4 +1,5 @@
 QuestionService/.env
+user-service/.env
 QuestionService/insert_questions_script.py
 
 # See https://help.github.com/articles/ignoring-files/ for more about ignoring files.

Backend/user-service/model/user-model.js

@@ -28,4 +28,4 @@ const UserModelSchema = new Schema({
   },
 });
 
-export default mongoose.model("UserModel", UserModelSchema);
+export default mongoose.model("UserModel", UserModelSchema, "Users");