Updating university section logic

[emrdagkusu]

For university endpoints, there is no "create section" option. There is only a "create lesson" option and its behavior: if there is no lesson with the given code, it creates a new lesson and creates the first section with given attributes. If there is a lesson with a given code, it directly creates a new section. We should have separate create section endpoint and we can use this endpoint with create lesson endpoint.