test: add comprehensive integration test suite for IAM platform

Add 162 integration tests covering authentication flows, TOTP MFA,
SSH key/certificate management, organization workflows, multi-org
access, self-service features, admin operations, authorization,
security edge cases, department/principal management, CA management,
policy compliance, WebAuthn passkeys, and ZeroTier network access.

Includes:
- Reusable API client library with session management
- Test fixtures for users, organizations, memberships, and CAs
- Helper functions for SSH key generation and verification
- Documentation for running and writing tests

Also update test configuration to disable conflicting maas plugins
and configure WebAuthn/session settings for localhost testing.

config/testing.py

@@ -30,7 +30,13 @@ class TestingConfig(BaseConfig):
 
     # Use different Redis DB for testing
     REDIS_URL = "redis://localhost:6379/15"
-    
+
     # Use filesystem for sessions in testing
     SESSION_TYPE = "filesystem"
     SESSION_FILE_DIR = "/tmp/flask_session_test"
+
+    # Override cookie domain so test_client on localhost can send cookies
+    SESSION_COOKIE_DOMAIN = None
+    WEBAUTHN_RP_ID = "localhost"
+    WEBAUTHN_ORIGIN = "http://localhost:8080"
+    FRONTEND_URL = "http://localhost:8080"