auth - update authreducer

export default (state = {}, action) => {
  switch (action.type) {
    // LOGIN => got login response => turn off loading state, put errors in state
    case 'LOGIN':
      return {
        ...state,
        inProgress: false,
        errors: action.error ? action.payload.errors : null
      };
    // ASYNC_START => made http request => set loading state
    case 'ASYNC_START':
      if (action.subtype === 'LOGIN' || action.subtype === 'REGISTER') {
        return { ...state, inProgress: true };
      }
      break;
    // UPDATE_FIELD_AUTH => new value in form field => update value in state
    case 'UPDATE_FIELD_AUTH':
      return { ...state, [action.key]: action.value };
    default:
      return state;
  }
};