feat: add unit and integration tests for rental management domain

- Introduced RentPaymentCorrectionTest and RentPaymentTest to validate payment and refund logic.
- Added PhoneNumberTest to ensure proper normalization of phone numbers.
- Created TenantTest to verify attachment management and tenant referencing.
- Implemented ReplacementRentalApiJourneyIT for end-to-end testing of rental and payment workflows.
- Documented architectural decisions in ADR-0014, emphasizing strict DDD boundaries and transaction management.

frontend/src/app/services/session.service.spec.ts

@@ -1,11 +1,11 @@
 import { HttpClient } from '@angular/common/http';
 import { TestBed } from '@angular/core/testing';
-import { of, Subject, throwError } from 'rxjs';
+import { NEVER, of, Subject, throwError } from 'rxjs';
 import { vi } from 'vitest';
 import { SessionService } from './session.service';
 
 describe('SessionService', () => {
-  const http = { get: vi.fn() };
+  const http = { get: vi.fn(), post: vi.fn() };
 
   beforeEach(() => {
     vi.clearAllMocks();
@@ -53,4 +53,15 @@ describe('SessionService', () => {
     expect(http.get).toHaveBeenCalledWith('/api/user');
     expect(service.username()).toBe('');
   });
+
+  it('posts logout with a truthful pending state', () => {
+    const service = TestBed.inject(SessionService);
+    service.status.set('authenticated');
+    http.post.mockReturnValueOnce(NEVER);
+
+    service.logout();
+
+    expect(service.status()).toBe('signing-out');
+    expect(http.post).toHaveBeenCalledWith('/logout', null, { responseType: 'text' });
+  });
 });