database.rules.json

{
  "rules": {
    ".read": "true",
    ".write": "auth != null",
    "users": {
      "$id": {
      	"info": {
          "level": {
            ".read": "true",
    		".write": "false"
          }
        }
      }
    },
    "pages": {
      ".indexOn": ["slug"]
    },
    "posts": {
      ".indexOn": ["slug"]
    },
    "courses": {
      ".indexOn": ["slug"]
    },
    "subjects": {
      ".indexOn": ["slug"]
    },
    "modules": {
      ".indexOn": ["slug"]
    },
    "activities": {
      ".indexOn": ["slug"]
    }
  }
}