Fix the login flashing sometimes

Race condition between being able to login via OIDC in the background,
and making first requests

UI/Web/src/app/_resolvers/oidc.resolver.ts

@@ -0,0 +1,16 @@
+import {ActivatedRouteSnapshot, Resolve, RouterStateSnapshot} from '@angular/router';
+import {Injectable} from "@angular/core";
+import {Observable, take} from "rxjs";
+import {OidcService} from "../_services/oidc.service";
+
+@Injectable({
+  providedIn: 'root'
+})
+export class OidcResolver implements Resolve<any> {
+
+  constructor(private oidcService: OidcService) {}
+
+  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<any> {
+    return this.oidcService.loaded$.pipe(take(1));
+  }
+}

UI/Web/src/app/_services/oidc.service.ts

@@ -1,6 +1,6 @@
 import {DestroyRef, effect, inject, Injectable, signal} from '@angular/core';
 import {OAuthErrorEvent, OAuthService} from "angular-oauth2-oidc";
-import {BehaviorSubject, from} from "rxjs";
+import {BehaviorSubject, from, Observable} from "rxjs";
 import {HttpClient} from "@angular/common/http";
 import {environment} from "../../environments/environment";
 import {OidcPublicConfig} from "../admin/_models/oidc-config";
@@ -23,6 +23,8 @@ export class OidcService {
 
   baseUrl = environment.apiUrl;
 
+  private readonly loaded = new BehaviorSubject<boolean>(false);
+  public readonly loaded$: Observable<boolean> = this.loaded.asObservable();
   private readonly _ready = signal(false);
   public readonly ready = this._ready.asReadonly();
   private readonly _settings = signal<OidcPublicConfig | undefined>(undefined);
@@ -42,6 +44,7 @@ export class OidcService {
 
     this.config().subscribe(oidcSetting => {
       if (!oidcSetting.authority) {
+        this.loaded.next(true);
         return
       }
 
@@ -72,9 +75,8 @@ export class OidcService {
       });
 
       from(this.oauth2.loadDiscoveryDocumentAndTryLogin()).subscribe({
-        next: success => {
-          if (!success) return;
-
+        next: _ => {
+          this.loaded.next(true);
           this._ready.set(true);
         },
         error: error => {

UI/Web/src/app/app-routing.module.ts

@@ -2,12 +2,19 @@ import {NgModule} from '@angular/core';
 import {PreloadAllModules, RouterModule, Routes} from '@angular/router';
 import {AuthGuard} from './_guards/auth.guard';
 import {LibraryAccessGuard} from './_guards/library-access.guard';
+import {OidcResolver} from "./_resolvers/oidc.resolver";
 
 const routes: Routes = [
   {
     path: '',
     canActivate: [AuthGuard],
     runGuardsAndResolvers: 'always',
+    resolve: {
+      // Require OIDC discovery to be loaded before launching the app
+      // making sure we don't flash the login screen because we've made request before we could auto login
+      // If no OIDC is set up, this will resolve after one request to the backend
+      _: OidcResolver,
+    },
     children: [
       {
         path: 'settings',