fix: TRUST_PROXY-Kommentar aktualisieren und Modus beim Start loggen

Die Kommentare beschrieben noch einen einzelnen Reverse-Proxy-Hop. Sie
beschreiben jetzt die Cloudflare/Traefik-Liste. Beim Start wird einmal
auf info-Level geloggt, ob Hop-Zahl, Liste oder der Default aktiv ist
(nur Anzahl, keine Adressen), damit eine fehlende Produktionseinstellung
auffaellt. Das Standardverhalten bleibt unveraendert.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Backend/src/app.config.spec.ts

@@ -0,0 +1,67 @@
+import { Logger } from '@nestjs/common';
+import type { NestExpressApplication } from '@nestjs/platform-express';
+import {
+  configureApp,
+  describeTrustProxy,
+  trustProxySetting,
+} from './app.config';
+
+describe('trustProxySetting', () => {
+  const original = process.env.TRUST_PROXY;
+  afterEach(() => {
+    if (original === undefined) delete process.env.TRUST_PROXY;
+    else process.env.TRUST_PROXY = original;
+  });
+
+  it('defaults to one hop when unset or blank', () => {
+    delete process.env.TRUST_PROXY;
+    expect(trustProxySetting()).toBe(1);
+    process.env.TRUST_PROXY = '  ';
+    expect(trustProxySetting()).toBe(1);
+  });
+
+  it('parses a number as hop count and anything else as a list', () => {
+    process.env.TRUST_PROXY = '2';
+    expect(trustProxySetting()).toBe(2);
+    process.env.TRUST_PROXY = 'loopback, 10.42.0.0/16';
+    expect(trustProxySetting()).toBe('loopback, 10.42.0.0/16');
+  });
+});
+
+describe('describeTrustProxy', () => {
+  it('reports the hop count mode and the default fallback', () => {
+    expect(describeTrustProxy(1, false)).toBe(
+      'TRUST_PROXY not set, using default of 1 trusted hop',
+    );
+    expect(describeTrustProxy(2, true)).toBe('TRUST_PROXY: 2 trusted hop(s)');
+  });
+
+  it('reports the list mode with entry count but not the entries', () => {
+    const text = describeTrustProxy(
+      'loopback, 10.42.0.0/16, 2400:cb00::/32',
+      true,
+    );
+    expect(text).toBe('TRUST_PROXY: list of 3 trusted proxy range(s)');
+  });
+});
+
+describe('configureApp trust proxy logging', () => {
+  it('logs the active mode once at startup', () => {
+    const log = jest.spyOn(Logger.prototype, 'log').mockImplementation();
+    const app = {
+      set: jest.fn(),
+      useBodyParser: jest.fn(),
+      use: jest.fn(),
+      useGlobalFilters: jest.fn(),
+      enableCors: jest.fn(),
+      setGlobalPrefix: jest.fn(),
+      enableVersioning: jest.fn(),
+      useGlobalPipes: jest.fn(),
+    };
+    configureApp(app as unknown as NestExpressApplication);
+    expect(
+      log.mock.calls.filter(([m]) => String(m).startsWith('TRUST_PROXY')),
+    ).toHaveLength(1);
+    log.mockRestore();
+  });
+});