Development: Improve build plan relationship

[krusche]

This PR affects setups with Gitlab CI (which is still experimental)

Checklist

General

• 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

• I followed the 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 implemented the changes with a good performance and prevented too many database calls.
• I documented the Java code using JavaDoc style.

Motivation and Context

At the moment, the relationship between ProgrammingExercise -> BuildPlan is not ideal, because it leads to additional database queries / joins in many situation due to the nature of a ManyToOne relationship.

As the build plan is only needed in 2-3 situations, it is favorable to store the unidirectional relationship on the other side: BuildPlan -> ProgrammingExercise as a OneToMany relationship

Description

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

Test that the Gitlab CI features are still working

Review Progress

Code Review

• Review 1
• Review 2

Manual Tests

• Test 1
• Test 2

[jpbernius]

I tested this locally and after the fix with the missing FETCH I can confirm that GitLab can build the pipelines based on the build plan fetched from the API.