Angular - service request either to server1 or server2 depending in user which will login

Currently for development I have this environment config:

export const environment = {
  production: false,
  envName: 'dev',
  apiEndpoint: 'https://url.to.server1/api/' 
};

In the module.service.ts services I use apoEndpoint like this:

myServiceMethod1(param: any): Observable<Array<Response>>  {
  return this.httpClient.get(environment.apiEndpoint + 'rest/service/url/...');

My problem now I have to solve is, there are two servers (server1 with endpoint https://url.to.server1/api/ and server2 with endpoint https://url.to.server2/api/) - exactly ident application but with different URLs.

If a user will login, first I have to show at server1 if this user exists and if not then I have to look up at server2. And if the user is stored in database of server2 than any further request in sevices should be with https://url.to.server2/api/. If user is stored in database of server1 than any further request should be done with https://url.to.server1/api/.

My question now would be how to do this in the best way?

You could define an InjectionToken and provide it through a factory for all the auth modules.

Auth Service

    import {mainServer, fallbackServer} from '@env';
    
    @Injectable('root')
    export class AuthService {
      private server: string;
    
      auth(credentials): Observable<unknown> {
        // resolve the server here
        // store the server in this.server
      }
     
    }

Injection Token and Factory Provider

    export const AUTH_API = new InjectionToken<string>('com.my.project');
    export const authApiProvider = {
      provide: AUTH_API,
      useFactory: () => {
        const authService = inject(AuthService);
        return authService.server;
      };
    }

Then, you can provide the AUTH_API using the authApiProvider on every module. Or you might create an interceptor that injects AUTH_API and sets it to every request.

Note

I would encourage you to put this logic outside the client behind a proxy server and have all your requests go to the server serving your app. This will increase security and prevent you from handling CORS problems.