Add code coverage configuration (phpunit.xml source filter), baseline coverage report (21.27% lines), gitignore coverage/ and .phpunit.result.cache; remove deprecated setAccessible() calls

tests/phpunit/ThesisCreateValidationTest.php

@@ -26,7 +26,6 @@ class ThesisCreateValidationTest extends TestCase
     private function validate(array $post, bool $adminMode = false): array
     {
         $ref = new ReflectionMethod(ThesisCreateController::class, 'validateAndSanitise');
-        $ref->setAccessible(true);
 
         $db = TestDatabase::getInstance();
         $ctrl = new ThesisCreateController($db);