Loading data with resolve guard

A resolve guard is a different kind of router guard, as mentioned in Chapter 6, Implementing Role-Based Navigation. A resolve guard can load necessary data for a component by reading record IDs from route parameters, asynchronously loading the data, and having it ready when the component activates and initializes.

The major advantages of a resolve guard include reusability of the loading logic, a reduction of boilerplate code, and the shedding of dependencies because the component can receive the data it needs without having to import any service:

1. Create a new user.resolve.ts class under user/user:

   src/app/user/user/user.resolve.ts
   import { inject } from '@angular/core'
   import { ActivatedRouteSnapshot, ResolveFn } from '@angular/router'
   import { catchError, map } from 'rxjs/operators'
   import { transformError } from '../../common/common'
   import { User } from './user'
   import { UserService...