Development: Extract plagiarism detection service

[jakubriegel]

Checklist

General

• I tested all changes and their related features with all corresponding user types 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) database calls.
• I followed the coding and design guidelines.
• I added multiple integration tests (Spring) related to the features (with a high test coverage).
• I documented the Java code using JavaDoc style.

Changes affecting Programming Exercises

• I tested all changes and their related features with all corresponding user types on Test Server 1 (Atlassian Suite).
• I tested all changes and their related features with all corresponding user types on Test Server 2 (Jenkins and Gitlab).

Motivation and Context

Plagiarism detection logic is distributed in controllers for each exercise type resources. This logic has a common domain and could be stored in a dedicated class. The current state will also require a copy&paste approach in case on implementing new triggers for plagiarism detection, like continuous plagiarism control.

Description

This PR introduces a common PlagiarismDetectionService which own all plagiarism checks related logic. This class is implemented using the code moved from ModelingExerciseResource, TextExerciseResource and ProgrammingExercisePlagiarismResource classes.

There is a new PlagarismDetectionConfig class, which holds the configuration for plagiarism checks. This is the first step that enables this config to be stored on the server, which will be necessary for the continuous plagiarism control in the future.

Steps for Testing

Prerequisites:

• 1 Instructor and 2 Students
• 1 programming, 1 modeling and 1 text exercise

1. Create very similar submission to each of 3 exercises from both user accounts.
2. Go to exercise manage page and click on Check plagiarism.
3. Run plagiarism detection wich default settings.
4. Verify that plagiarism results are shown.
5. Run plagiarism detection wich similarity threshold changed to 100%.
6. Verify that no plagiarism result is shown.

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
• Code Review 2

Manual Tests

• Test 1
• Test 2

Test Coverage

Class/File	Line Coverage	Confirmation (assert/expect)
PlagiarismDetectionService	100%	✅

[MarkusPaulsen]

Code looks good + Tested on TS1