An in-memory auth service

Now, let’s implement a concrete version of the auth service that we can use:

1. Start by installing a JWT decoding library and, to fake authentication, a JWT encoding library:

   $ npm install fake-jwt-sign
   

2. Extend the abstract AuthService:

   src/app/auth/auth.in-memory.service.ts
   import { AuthService } from './auth.service'
   @Injectable({ providedIn: 'root' })
   export class InMemoryAuthService extends AuthService {
     constructor() {
       super()
       console.warn(
         'You're using the InMemoryAuthService. Do not use this service in production.'
       )
     }
     …
   }
   

3. Implement a fake authProvider function that simulates the authentication process, including creating a fake JWT on the fly:

   src/app/auth/auth.in-memory.service.ts
     import { sign } from 'fake-jwt-sign'//For InMemoryAuthService only
   ...
     protected authProvider(
       email: string,
       password...