Development: Avoid unnecessary fetching of messages and posts

[lennart-keller]

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.

Client

• Important: I implemented the changes with a very good performance, prevented too many (unnecessary) REST calls and made sure the UI is responsive, even with large data.
• I followed the coding and design guidelines.
• Following the theming guidelines, I specified colors only in the theming variable files and checked that the changes look consistent in both the light and the dark theme.
• I added multiple integration tests (Jest) related to the features (with a high test coverage), while following the test guidelines.
• I documented the TypeScript code using JSDoc style.

Motivation and Context

When a client receives a new or updated Q&A post or conversation message via WebSocket, it currently fetches the last 50 messages, despite the WebSocket message providing all necessary information for appropriate client updates. Particularly when numerous users are online simultaneously, this approach generates a substantial number of unnecessary GET requests that the servers must process.

Description

Upon receiving a WebSocket message for an updated or created post/message, the client now updates the list of stored posts/messages accordingly without triggering an unnecessary REST request. The only exception is, when new Q&A posts are received. Adapting this use case would require to implement the server-side filtering in the client-side. However, since this use case is deprecated, it will not be changed in this PR.

Steps for Testing

Prerequisites:

• 2 Students
• 1 Course with messaging and communication

1. Write messages/posts. Also react, edit, reply, and resolve messages/posts
2. Confirm (with the help of the Chrome developer tools) that GET /posts or GET /messages requests are only made (besides loading a page initially) if:
   1. another conversation is opened on the messages tab
   2. a new Q&A post is created (communication tab)
   3. you search for messages/posts or change other filtering settings

In all other cases, neither the author nor another involved course member (2nd student) makes GET requests

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

Client

Class/File	Line Coverage	Confirmation (assert/expect)
course-discussion.component.ts	95.28%	✅
metis.service.ts	95.58%	✅

Screenshots

No major UI changes (just a bugfix, because the post context filter was transparent):
before:

after:

[github-actions]

❌ Unable to deploy to test servers ❌

Testserver "artemis-test5.artemis.cit.tum.de" is already in use by PR #7358.

[basak-akan]

Tested on TS2.

• Writing messages/posts, reacting, editing, replying, and resolving messages worked as expected.
• GET /posts or GET /messages requests are only made for given situations

[MaximilianAnzinger]

code lgtm

[terlan98]

Tested on TS2. Works as expected 👍

[valentin-boehm]

lgtm