feat: add OIDC_CLIENT_SECRET configuration to frontend environment and OIDC provider settings

frontend/src/app/app.config.ts

@@ -20,6 +20,7 @@ export const appConfig: ApplicationConfig = {
           issuer: configService.oidcIssuer,
           redirectUri: window.location.origin + '/',
           clientId: configService.clientId,
+          dummyClientSecret: configService.clientSecret,
           responseType: 'code',
           scope: 'openid profile email',
           showDebugInformation: true,

frontend/src/app/config.service.ts

@@ -15,4 +15,8 @@ export class ConfigService {
   get clientId(): string {
     return import.meta.env['OIDC_CLIENT_ID'] || 'lmnp-client';
   }
+
+  get clientSecret(): string {
+    return import.meta.env['OIDC_CLIENT_SECRET'] || 'lmnp-secret';
+  }
 }