Add injectable token provider for authenticated endpoints

[itslenny]

Hi, we have a scenario where some of our endpoints are secured and some are not.

Using the interceptor pattern leaves us unable to determine if we should add the authorize header or not. As a solution I added an injectable angular token provider.

Basically... if there are "authorization" header values AND the auth type is set to bearer in the swagger file it won't include those as params that are needed to be provided by the API consumer, and will instead try to fetch the token using the api token provider as needed. Additionally, we have two different types of auth tokens authorization and device-authorization so this enables us to provide the correct token based on what the endpoint defines in the swagger file.

With this pattern we only append the auth header if it is required, and the individual places that we call the api service don't need to have or even know about the token.

This could be merged as-is, but I think it'd cause some breaking changes for anyone depending on sending auth tokens as a param. Perhaps i can be a cli flag?

We're using the forked version as-is, but I just wanted to push this change upstream in case you'd like to incorporate it or if anyone else may need similar functionality.

Usage...

add this to your app module

{ provide: ApiServiceTokenProviderInjectionToken, useClass: ApiTokenProviderServiceService },

create a provider service like this...

@Injectable()
export class ApiTokenProviderServiceService implements ApiServiceTokenProvider {

  getToken(name: string): Observable<string> {
    switch (name) {
      case 'authorization':
        // TODO: get token from wherever it is stored
        return of('');
      case 'device-authorization':
        // optional secondary auth types
        return of('');
      default:
        // unknown auth type
        return of(null);
    }
  }
}