Design a GraphQL Schema

Design a GraphQL schema for [APPLICATION TYPE].

Application context:
- What it does: [BRIEF DESCRIPTION]
- Main entities: [LIST YOUR CORE DATA MODELS — e.g. User, Product, Order, etc.]
- Key relationships: [DESCRIBE HOW ENTITIES RELATE]
- Operations needed:
  - Queries: [LIST WHAT NEEDS TO BE FETCHED]
  - Mutations: [LIST WHAT NEEDS TO BE CREATED/UPDATED/DELETED]
  - Subscriptions (if any): [REAL-TIME EVENTS NEEDED]

Please provide:
1. Full schema definition in SDL (Schema Definition Language)
2. Key design decisions explained (type choices, nullable fields, pagination approach)
3. Example queries and mutations for the main use cases
4. Resolver structure recommendations
5. Any N+1 problem areas and how to address them (DataLoader suggestions)