first version with linter fixes

composer.json

composer.lock

phpstan.neon

src/API/CourseProviderInterface.php

src/Command/TestCommand.php

src/Controller/GetCoursesByOrganization.php

src/Controller/GetCoursesByPerson.php

src/Controller/GetExamsByCourse.php

src/Controller/GetStudentsByCourse.php

src/Controller/LoggedInOnly.php

src/DataPersister/CourseDataPersister.php

src/DataProvider/CourseCollectionDataProvider.php

src/DataProvider/CourseItemDataProvider.php

src/DependencyInjection/Configuration.php

src/DependencyInjection/DbpRelayCourseExtension.php

src/Entity/Course.php

src/Entity/CourseAttendee.php

src/Entity/Exam.php

src/Service/CourseProviderInterface.php

src/Service/DummyCourseProvider.php