State Shape

{
  entities: {
    challenges: {
      id: 1,
      title: "Merge Sort",
      skeleton: `
      const mergeSort = function mergeSort(array) { 

      }
      const merge = function merge(array1, array2){

      } `,
      tests: [
        1: `....`,
        2: `....`,
        3: `....`
      ],
      solution: "..."
    },
  },
  user: {
    id: 1,
    username: "gtongue",
    files: [1,5,6],
    completed: [1,3,5]
  },
  files: {
    1: {
      id: 1,
      name: `...`,
      content: `...`
    }
  }
  ui: {
    loading: true/false
  },
  errors: {
    login: ["Incorrect username/password combination"]
  },
  session: {
    id: 4,
    username: "gtongue",
    user_id: 1
  }
}