gistfile1.js

// User Model

attributes: {
  username: {
    type: 'string',
    required: true,
    unique: true,   
  },
  sender: {
    model: conversation
  },
  recipient: {
    model: conversation
  }
}

// Conversation model

attributes: {
  
  messages: {
    collection: 'message',
    via: 'conversation'
  }
}

// Message model

attributes: {
  text: {
    type: 'string'
  },
  conversation: {
    model: 'conversation'
  },  	
}