fix: Major bug cleanup pass 1

toju-app/src/app/domains/authentication/domain/logic/signal-server-provision.rules.spec.ts

@@ -0,0 +1,36 @@
+import {
+  describe,
+  it,
+  expect
+} from 'vitest';
+import {
+  ProvisionUsernameCollisionError,
+  buildProvisionUsernameCandidates,
+  shortHomeUserId
+} from './signal-server-provision.rules';
+
+describe('signal-server-provision.rules', () => {
+  it('derives a stable short id from a home user uuid', () => {
+    expect(shortHomeUserId('a3f2b1c4-5678-90ab-cdef-1234567890ab')).toBe('a3f2b1');
+  });
+
+  it('orders username candidates with preferred first then suffixed fallback', () => {
+    expect(
+      buildProvisionUsernameCandidates('alice', 'a3f2b1c4-5678-90ab-cdef-1234567890ab')
+    ).toEqual(['alice', 'alice-a3f2b1']);
+  });
+
+  it('deduplicates candidates when suffix would repeat preferred username', () => {
+    expect(
+      buildProvisionUsernameCandidates('alice-a3f2b1', 'a3f2b1c4-5678-90ab-cdef-1234567890ab')
+    ).toEqual(['alice-a3f2b1']);
+  });
+
+  it('exposes attempted usernames on collision errors', () => {
+    const error = new ProvisionUsernameCollisionError('https://signal.example.com', ['alice', 'alice-a3f2b1']);
+
+    expect(error.name).toBe('ProvisionUsernameCollisionError');
+    expect(error.serverUrl).toBe('https://signal.example.com');
+    expect(error.attemptedUsernames).toEqual(['alice', 'alice-a3f2b1']);
+  });
+});