Communication: Fix Tagging other Users does not work

[FelberMartin]

This resolves issue #65

Now using a different API endpoint for searching tag candidates (matching iOS and WebApp behaviour).

Out of Scope
While testing the implementation I found minor bugs / chances to improve the UI/UX, but I will create a separate issue #72 for this. This PR only focusses on the functionality.

[julian-wls]

Just tested it and it works as expected. Good work!

The only thing I noticed is, that the preview doesn't get rendered after clicking on the preview button. However, this seems like a topic for another PR in my opinion as it is not really related to the topic of this PR and more related to markdown rendering.

Good to be merged from my side!

[TimOrtel]

Please add a UI test for this tagging behaviour. Also add an integration test that checks that the application can talk to the server properly.

[FelberMartin]

Also add an integration test that checks that the application can talk to the server properly.

@TimOrtel Could you elaborate, please? I am not sure what you mean by "the application can talk to the server properly". Should this just be a generic test whether the ConversationViewModel can communicate with a MockServer via requestReload() or should the test somehow be tailored to the tagging behaviour? If so, how?

[TimOrtel]

Please also add tests that verify:

• Initially the auto complete hints are not displayed
• when entering text that is not @ then the auto complete hints are not displayed
• when entering an @ the hints are displayed but when removing the @ again the hints are no longer displayed
• auto completing can be used twice in a row

[TimOrtel]

Also add an integration test that checks that the application can talk to the server properly.

@TimOrtel Could you elaborate, please? I am not sure what you mean by "the application can talk to the server properly". Should this just be a generic test whether the ConversationViewModel can communicate with a MockServer via requestReload() or should the test somehow be tailored to the tagging behaviour? If so, how?

You can see exemplary integration tests in feature/metis/conversation/src/test/kotlin/de/tum/informatics/www1/artemis/native_app/feature/metis/conversation/ConversationAnswerMessagesE2eTest.kt

[TimOrtel]

The code looks good to me.