Resolve "The owner of a question or answer can delete them if they are not important or validated"

Description

Before this feature, only the course owner can delete a question or a response. Now, the author of the question or the response can delete it if they are not important or validated.

Migration and compatibility

• The merge request DOES NOT update the models. If it does, database migrations are needed after merging, add the label Database migrations
• The merge request DOES NOT break the compatibility.

TODO

Before being accepted, any merge request must fulfill the following requirements:

• Check PEP8 writing style as described in CONTRIBUTING.md.
• Ensure existing tests are still working properly.
• Features have been tested.
• Every translatable strings are written in proper english.
• Every translatable strings are tagged for translation using gettext, blocktrans and/or trans.
• Ensure that there is no side effect in files: changes are only related to one, and only one feature.
• Ensure that no file has been removed by accident.
• API is documented, as well as the behavior, if needed, in docs.
• Ensure the commit history is “clean enough” (this means no extra merge commits, etc).
• Ensure pipeline succeeds.

Steps to Test or Reproduce

(outline the steps to test or reproduce the merge request here. First, ensure there is not commit waiting to be pushed)

git checkout <feature_branch>  # Switch to the feature branch
git fetch --all --prune  # Download new commits
git reset --hard <remote>/<feature_branch>  # Override your local worktree with the one from remote branch

Impacted Areas in Application

(list general components of the application that this merge request will affect)

/label Status::In development /label Needs review