Development: Add additional tags to active user metrics

[b-fein]

Note

Stacked on top of #7229

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 documented the Java code using JavaDoc style.

Motivation and Context

It might happen that the same course names and/or exam names are used multiple times in different semesters. This makes the tags non-unique and only the metrics for one of the courses/exams with the duplicate title are returned.

Description

• Adds the courseId tag to both the course and exam metrics since we can be sure that those are unique.
• Additionally refactors the code a bit to make it more readable.
• Improves a database query to move the counting to the database to avoid loading the objects.

Steps for Testing

Same as in #7229, optional.

Review Progress

Performance Review

• 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

Test Coverage

Class/File	Line Coverage	Confirmation (assert/expect)
MetricsBean.java	87%, 100% for changed code	✅

[sleiss]

Code LGTM