add module import checks

src/lib/loading/loading.module.ts

@@ -1,4 +1,4 @@
-import { ModuleWithProviders, NgModule } from '@angular/core';
+import { ModuleWithProviders, NgModule, Optional } from '@angular/core';
 import { FullPageLoadingIndicatorComponent } from './full-page-loading-indicator/full-page-loading-indicator.component';
 import { ProgressLoadingComponent } from './progress-loading/progress-loading.component';
 import { LoadingService } from './loading.service';
@@ -17,6 +17,12 @@ const components = [FullPageLoadingIndicatorComponent, ProgressLoadingComponent,
     imports: [MatProgressSpinnerModule, CommonModule, MatProgressBarModule, MatIconModule, TranslateModule],
 })
 export class IqserLoadingModule {
+    constructor(@Optional() loadingService: LoadingService) {
+        if (!loadingService) {
+            throw new Error('Call forRoot() in AppModule to use IqserLoadingModule');
+        }
+    }
+
     static forRoot(): ModuleWithProviders<IqserLoadingModule> {
         return {
             ngModule: IqserLoadingModule,

src/lib/translations/iqser-translate.module.ts

@@ -1,4 +1,4 @@
-import { ModuleWithProviders, NgModule } from '@angular/core';
+import { Inject, ModuleWithProviders, NgModule, Optional } from '@angular/core';
 import { TranslateCompiler, TranslateLoader, TranslateModule } from '@ngx-translate/core';
 import { TranslateMessageFormatCompiler } from 'ngx-translate-messageformat-compiler';
 import { pruningTranslationLoaderFactory } from './http-loader-factory';
@@ -22,6 +22,12 @@ const translateLoaderToken = 'translateLoader';
     exports: [TranslateModule],
 })
 export class IqserTranslateModule {
+    constructor(@Optional() @Inject(translateLoaderToken) translateLoader: TranslateLoader) {
+        if (!translateLoader) {
+            throw new Error('Call forRoot() in AppModule to use IqserTranslateModule');
+        }
+    }
+
     static forRoot(options?: IqserTranslateModuleOptions): ModuleWithProviders<IqserTranslateModule> {
         return {
             ngModule: IqserTranslateModule,