Creating an auth service

We will start by creating the abstract auth service and the in-memory service:

1. Add an auth service:

   $ npx ng g s auth --flat false
   $ npx ng g s auth/inMemoryAuth --skip-tests
   

2. Rename in-memory-auth.service.ts to auth.in-memory.service.ts so that the different auth providers visually group together in File Explorer.
3. Remove the @Injectable() decorator of auth.service.ts , but keep it on auth.in-memory.service.ts.
4. Ensure that authService is provided in app.module.ts and that InMemoryAuthService is used and not the abstract class:

   src/app/app.module.ts
   import { AuthService } from './auth/auth.service'
   import { InMemoryAuthService } from './auth/auth.in-memory.service'
   ...
     providers: [
       {
         provide: AuthService,
         useClass: InMemoryAuthService
       },
       ...
   ]
   

Creating a separate folder for the service organizes various components related to auth, such as the enum...