Development: Minimize messages response payload

[lennart-keller]

Checklist

General

• I tested all changes and their related features with all corresponding user types 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 documented the Java code using JavaDoc style.

Motivation and Context

Following #6964 we would like to decrease the payload of the messaging endpoints even further to increase performance. This PR reduces the size of the conversation Object attached to posts.

In a follow-up PR, the conversation object will be set to null completely.

Description

For GET .../messages, the .hideDetails() method from #6964 is applied to the conversation of the returned posts, including the answers. Also for the endpoints to retrieve the channel for an exercise/lecture this method is invoked.

Steps for Testing

Prerequisites:

• 1 student
• 1 course with messaging enabled

1. Open the developer tools inspecting the REST calls
2. Visit the messages tab and click on a channel to load messages (write some if necessary)
3. Confirm, that the conversation objects attached to messages in the response contains only minimal information, i.e. no exercise, no lecture, no exam, no course, no conversation participants
4. The same should apply to the post object attached to answers of a message (write some answers if necessary)
5. Confirm that you can create/edit/delete/react to messages and also create/edit/delete/react to answers
6. Repeat step 5 for the lecture and exercise page for a lecture/exercise with an attached channel and look at the /channel responses as well
7. Repeat step 2-4 for group chats and direct messages

Review Progress

Performance Review

• I confirm that the client changes (in particular related to REST calls and UI responsiveness) are implemented with a very good performance
• I 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)
BaseExercise.java	98%	✅
Exercise.java	91%	✅
FileUploadExercise.java	100%	✅
FileUploadSubmission.java	100%	✅
ProgrammingExercise.java	92%	✅
ProgrammingSubmission.java	100%	✅
TextExercise.java	100%	✅
TextSubmission.java	98%	✅
ModelingExercise.java	93%	✅
ModelingSubmission.java	92%	✅
DragAndDropQuestion.java	84%	✅
DragAndDropQuestionStatistic.java	98%	✅
DragAndDropSubmittedAnswer.java	91%	✅
MultipleChoiceQuestion.java	88%	✅
MultipleChoiceQuestionStatistic.java	99%	✅
MultipleChoiceSubmittedAnswer.java	93%	✅
QuizExercise.java	90%	✅
QuizQuestion.java	96%	✅
QuizSubmission.java	100%	✅
ShortAnswerQuestion.java	87%	✅
ShortAnswerQuestionStatistic.java	99%	✅
ShortAnswerSubmittedAnswer.java	87%	✅
ConversationMessageResource.java	97%	✅

[TimOrtel]

LGTM. Very nice improvement.

[tobias-lippert]

Tested on ts5. Sending messages is still possible and the payload seems to be almost minimal.
I only noticed that the response for /conversations contains the type property twice for each conversation and I don't know if this is caused by this PR and can lead to problems.

[lennart-keller]

Tested on ts5. Sending messages is still possible and the payload seems to be almost minimal.
I only noticed that the response for /conversations contains the type property twice for each conversation and I don't know if this is caused by this PR and can lead to problems.

The duplicate type property is not introduced by this PR

[Strohgelaender]

code

[tobias-lippert]

Tested on ts5. Still works after removing more content from the response body.

[RY997]

Tested on ts5, the number of REST calls looks good for me

[laadvo]

tested on ts1, the response payload is now a lot smaller. Writing messages, replies and reacting to them still works