Fix tests

- Fix InstallerTest case
- Fix native function mocking
- Add returntype for Unit-Tests
- Fixing ExtendedPDO test troubles
- Fix wrong class inheritance path for DatabaseTestTrait.php
- Fix SyslogLogger Server Exception for PHP8
- Add user/contact to database.fixture.php
- Avoid invalid rollbacks for test setup in PHP8

tests/FixtureTest.php

@@ -26,7 +26,7 @@ abstract class FixtureTest extends DatabaseTest
 	/**
 	 * Create variables used by tests.
 	 */
-	protected function setUp()
+	protected function setUp() : void
 	{
 		parent::setUp();