Adaptive learning: Extend learning path feature to recommend sequence of lecture units and exercises

[MaximilianAnzinger]

⚠️ Stacked on #7091 please don't merge accidentally

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) 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 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.

Motivation and Context

We want to provide a sequential order of lecture units and exercises for students participating via the learning paths feature.

Description

This PR adds the second half for generating this sequential order by recommending an order of learning objects within the competencies.
The LearningPathService is now split into the LearningPathService that should be used by other components and the sub-services LearningPathRecommendationService and LearningPathNgxSercive that handle the corresponding sub-tasks.
In addition to recommending an order of competencies, the recommendation now includes a suggested order of the learning objects (lecture units and exercises). The recommender will select exercises by difficulty level according to the prior performance of the student and also recommend repetitions of already completed exercises if the achieved score is comparably low.

Steps for Testing

Prerequisites:

• 1 Instructor
• 1 Student
• 1 Course with at least one competency and learning paths enabled
• exercises and lecture units for each type linked to competency

1. Log in to Artemis as Student
2. Navigate to the Learning Path participation view in the course
3. Make sure the visualized graph on the left side of your screen is displayed as expected (no mastered competencies displayed, the competencies are ordered sequentially/a chain from top to bottom excluding the nodes for the learning objects, and the recommended lecture units/exercises are a linear chain between the competency start and end nodes)

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

Server

Class/File	Line Coverage	Confirmation (assert/expect)
CompetencyProgressService.java	91%	✅
CourseService.java	89%	✅
ExerciseService.java	96%	✅
LearningObjectService.java	89%	✅
ParticipantScoreService.java	96%	✅
LearningPathNgxService.java	97%	✅
LearningPathRecommendationService.java	98%	✅
LearningPathService.java	98%	✅
CompetencyResource.java	97%	✅
CourseResource.java	94%	✅
LearningPathResource.java	91%	✅

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Screenshots

As this PR doesn't change the UI there are no screenshots of shiny new components, just a comparison between the old graph received from the server (in participation view) and the new one:

Previously:

Now (excludes completed exercises and displays linear path):

The base branch was changed.

[JohannesStoehr]

Reapprove Code after merges

[Strohgelaender]

code lgtm

[tobias-lippert]

Tested in testing session on ts1.

[nityanandaz]

Code looks fine

[florian-glombik]

Tested on ts1, the described use case worked fine (split path is now displayed sequentially)

A view points out of scope for this PR:

• the continue button was always disabled (not quite sure if the up down arrow solution is in another PR)
• I did not understand how to delete and modify competency relations
• Deleting a competency that is linked via relation did not work (400 as response)

[MaximilianAnzinger]

@florian-glombik thank you for your review 👍

• the continue button was always disabled (not quite sure if the up down arrow solution is in another PR)

the continue button & sidebar is reworked and fixed in #7235

• I did not understand how to delete and modify competency relations

this is unrelated to this PR, but you can click on the respective edge and delete it that way.

• Deleting a competency that is linked via relation did not work (400 as response)

do you know if this is also the case on develop? I'll take a look at it but this is an unrelated issue.