const appRoutes: Routes = [
    { path: '', redirectTo: '/login', pathMatch: 'full' },
    { path: 'page1', component: Page1Component },  // can't use RouterStringService here I don't think...
    { path: 'page2', component: Page2Component }
]
@NgModule({...})
export class AppRouting Module {}

// changes to above code block
{ path: 'page1', redirectTo: 'new-page1' },
{ path: 'new-page1', component NewPage1Component },

export class RouterStringService {
    static page1: string = '/page1'
    static page2: string = '/page2

    // put string builders here too for things like /pageX/:id

    constructor() {}
}

export const AppUrls = {
    base: "...",
    login: "...",
    ...
}

const appRoutes: Routes = [
    { path: '', redirectTo: AppUrls.login, pathMatch: 'full' },

import {AppUrls} from '....';

@Component({
  selector: '...
})
export class SomeComponent implements OnInit {

  AppUrls = AppUrls;

[routerLink]="{{AppUrls.login}}"