将 SAP Spartacus 作为 feature module 进行 Lazy Load 延迟加载时，遇到如下错误：
ERROR Error: Uncaught (in promise): NullInjectorError: R3InjectorError(CatalogModule)[UserAuthEventModule -> UserAuthEventBuilder -> UserAuthEventBuilder -> AuthService -> OAuthLibWrapperService -> OAuthService -> OAuthService -> OAuthService]: NullInjectorError: No provider for OAuthService! NullInjectorError: R3InjectorError(CatalogModule)[UserAuthEventModule -> UserAuthEventBuilder -> UserAuthEventBuilder -> AuthService -> OAuthLibWrapperService -> OAuthService -> OAuthService -> OAuthService]: NullInjectorError: No provider for OAuthService! at NullInjector.get (core.js:11120:1) at R3Injector.get (core.js:11287:1) at R3Injector.get (core.js:11287:1) at R3Injector.get (core.js:11287:1) at injectInjectorOnly (core.js:4770:1) at Module.ɵɵinject (core.js:4774:1) at Object.OAuthLibWrapperService_Factory [as factory] (spartacus-core.js:1514:1) at R3Injector.hydrate (core.js:11457:1) at R3Injector.get (core.js:11276:1) at injectInjectorOnly (core.js:4770:1) at resolvePromise (zone.js:1211:1) at resolvePromise (zone.js:1165:1) at zone.js:1278:1 at _ZoneDelegate.invokeTask (zone.js:406:1) at Object.onInvokeTask (core.js:28679:1) at _ZoneDelegate.invokeTask (zone.js:405:1) at Zone.runTask (zone.js:178:1) at drainMicroTaskQueue (zone.js:585:1)UserAuthEventModule
具体分析：
UserAuthEventModule 使用了 UserAuthEventBuilder 作为依赖：
UserAuthEventBuilder 使用了 AuthService：
AuthService 使用了 OAuthLibWrapperService
OAuthLibWrapperService 使用了 OAuthService
这个 OAuthService 最后来自 angular-oauth2-oidc，一个开源的 Angular oAuth2 实现库：
OAuthService angular-oauth2-oidc
根据错误消息 No provider for OAuthService 在网上查找，发现下列这个 known issue：
https://github.com/manfredsteyer/angular-oauth2-oidc/issues/258
添加第 49 行的 OAuthModule.forRoot() 后，错误消失：
https://github.com/manfredsteyer/angular-oauth2-oidc/issues/241
UserAuthEventModule 被 UserAuthModule 所 import：
UserAuthModule 最后通过 index.ts 导出：
遇到新的错误：
ERROR Error: Uncaught (in promise): NullInjectorError: R3InjectorError(CatalogModule)[EffectsFeatureModule -> InjectionToken @ngrx/effects Feature Effects -> [object Object] -> LanguagesEffects -> SiteConnector -> SiteConnector -> SiteAdapter -> SiteAdapter -> SiteAdapter]: NullInjectorError: No provider for SiteAdapter! NullInjectorError: R3InjectorError(CatalogModule)[EffectsFeatureModule -> InjectionToken @ngrx/effects Feature Effects -> [object Object] -> LanguagesEffects -> SiteConnector -> SiteConnector -> SiteAdapter -> SiteAdapter -> SiteAdapter]: NullInjectorError: No provider for SiteAdapter! at NullInjector.get (core.js:11120:1) at R3Injector.get (core.js:11287:1) at R3Injector.get (core.js:11287:1) at R3Injector.get (core.js:11287:1) at injectInjectorOnly (core.js:4770:1) at Module.ɵɵinject (core.js:4774:1) at Object.SiteConnector_Factory [as factory] (spartacus-core.js:7506:1) at R3Injector.hydrate (core.js:11457:1) at R3Injector.get (core.js:11276:1) at NgModuleRef$1.get (core.js:25352:1) at resolvePromise (zone.js:1211:1) at resolvePromise (zone.js:1165:1) at zone.js:1278:1 at _ZoneDelegate.invokeTask (zone.js:406:1) at Object.onInvokeTask (core.js:28679:1) at _ZoneDelegate.invokeTask (zone.js:405:1) at Zone.runTask (zone.js:178:1) at drainMicroTaskQueue (zone.js:585:1)
很多 forRoot 方法：
Minor 版本的更改，意味着我们添加了新功能，但它们默认配置为关闭，以免导致兼容性问题。 新的 Minor 版本还意味着包含可能影响兼容性的更改或错误修复，但这些也由功能标志控制。 因此，所有重大变化都是“选择加入（Opt-in）”。
