General: Improve performance of overview page

[krusche]

Checklist

General

• I tested all changes and their related features with all corresponding user types on a test server.
• This is a small issue that I tested locally and was confirmed by another developer on a test server.
• I chose a title conforming to the naming conventions for pull requests.

Server

• Important: I implemented the changes with a very good performance and prevented too many (unnecessary) database calls.
• I followed the coding and design guidelines.
• I documented the Java code using JavaDoc style.

Client

• Important: I implemented the changes with a very good performance, prevented too many (unnecessary) REST calls and made sure the UI is responsive, even with large data.
• I followed the coding and design guidelines.

Motivation and Context

We're sending too much data in the for-dashboard call of the overview page that is not needed.

Description

Removed fields from the transmitted courses that are not relevant. Active exams are now added separately so we can still display active exams on top.

Steps for Testing

Prerequisites:

• 1 Student

1. Log in to Artemis
2. Click into one course
3. Make sure all data is displayed correctly

Review Progress

Performance Review

• I (as a reviewer) confirm that the client changes (in particular related to REST calls and UI responsiveness) are implemented with a very good performance
• I (as a reviewer) confirm that the server changes (in particular related to database calls) are implemented with a very good performance

Code Review

• Code Review 1

Manual Tests

• Test 1

[bassner]

Tested locally and on TS2, looks good so far