Development: Remove Gitlab support

[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.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• 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) and too complex database calls.
• I strictly followed the principle of data economy for all database calls.
• I strictly followed the server coding and design guidelines.
• I added multiple integration tests (Spring) related to the features (with a high test coverage).
• I added pre-authorization annotations according to the guidelines and checked the course groups for all new REST Calls (security).
• 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 (e.g. using paging).
• I strictly followed the principle of data economy for all client-server REST calls.
• I strictly followed the client coding and design guidelines.
• Following the theming guidelines, I specified colors only in the theming variable files and checked that the changes look consistent in both the light and the dark theme.
• I added multiple integration tests (Jest) related to the features (with a high test coverage), while following the test guidelines.
• I added authorities to all new routes and checked the course groups for displaying navigation elements (links, buttons).
• I documented the TypeScript code using JSDoc style.
• I added multiple screenshots/screencasts of my UI changes.
• I translated all newly inserted strings into English and German.

Changes affecting Programming Exercises

• High priority: I tested all changes and their related features with all corresponding user types on a test server configured with the integrated lifecycle setup (LocalVC and LocalCI).
• I tested all changes and their related features with all corresponding user types on a test server configured with Gitlab and Jenkins.

Motivation and Context

Description

• This PR also removes all lock and unlock operations, because they are not needed anymore
• It simplifies the VersionControlInterface

TODO:

• Make sure locked repositories are displayed correctly in the online code editor, based on the different conditions (in particular when it comes to submission policies)
• Make sure all those conditions are taken into account during push operations
• Reimplement the schedule for stash operations in a meaningful way (without coupling them to lock operations)
• Remove localVcEnabled in the client (and potentially on the server) to simplify the code, as this is now the only supported option

Steps for Testing

Prerequisites:

• 1 Instructor
• 2 Students
• 1 Programming Exercise with Complaints enabled

1. Log in to Artemis
2. Navigate to Course Administration
3. ...

Exam Mode Testing

Prerequisites:

• 1 Instructor
• 2 Students
• 1 Exam with a Programming Exercise

1. Log in to Artemis
2. Participate in the exam as a student
3. Make sure that the UI of the programming exercise in the exam mode stays unchanged. You can use the exam mode documentation as reference.
4. ...

Testserver States

You can manage test servers using Helios. Check environment statuses in the environment list. To deploy to a test server, go to the CI/CD page, find your PR or branch, and trigger the deployment.

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 even for very large courses with more than 2000 students.
• I (as a reviewer) confirm that the server changes (in particular related to database calls) are implemented with a very good performance even for very large courses with more than 2000 students.

Code Review

• Code Review 1
• Code Review 2

Manual Tests

• Test 1
• Test 2

Exam Mode Test

• Test 1
• Test 2

Performance Tests

• Test 1
• Test 2

Test Coverage

Screenshots