[Groups] Streamline group self-enrollment for students

[tobe_baeyens]

Problem: Currently, students enrolling in groups face challenges in locating the correct groups due to the extensive scrolling and limited organization on the enrollment page. Instructors, in contrast, have access to a tabbed interface that helps organize groups by set.

I propose the following enhancements:

• Single enrollment page per group set: Create a dedicated page for each group set that students can access to enroll in groups within that set only, reducing confusion and unnecessary navigation.
• Automated student invitation to enrollment page: Enable instructors to automatically invite students to this enrollment page, guiding them directly to the relevant group set and bypassing unrelated groups.
• Persistent link in group set settings: Provide instructors with a persistent link to the enrollment page in group set settings. This link can be shared multiple times with students, ensuring they can easily access the correct group set enrollment page if needed.