This pull request adds participant management features to the Mergington High School Activities app, allowing users to view, add, and remove participants from activities. It also introduces comprehensive backend tests to ensure API reliability. The main changes include expanding the activities list, implementing participant removal in both backend and frontend, updating the UI to show participants, and adding thorough automated tests.

Backend functionality:

• Added a new DELETE endpoint (/activities/{activity_name}/participants/{email}) in app.py to allow removal of participants from activities, with appropriate error handling for non-existent activities or participants.
• Enhanced the signup endpoint to prevent duplicate signups by checking if the student is already registered for the activity.
• Expanded the activities data structure with additional activities and participants for more realistic scenarios.

Frontend/UI improvements:

• Updated the activity cards in app.js to display a list of participants for each activity, with a delete button next to each participant for removal.
• Implemented frontend logic to handle participant removal via DELETE requests and to refresh the activities list after changes. [1] [2]
• Added new CSS styles in styles.css for the participants list and delete button to improve usability and appearance.

Testing:

• Introduced a new test suite (test_app.py) with fixtures to reset activity data and comprehensive tests for all endpoints, including participant addition and removal, error cases, and data integrity.