Issue #3275943 by alex.ksis: Reset cache of the commented entity.

[ksis]

Problem

Moderators do not see new comments in a discussion until cache is flushed.

Solution

Reset discussion cache after a new comment was posted.

Issue tracker

• https://www.drupal.org/project/social/issues/3275943
• https://getopensocial.atlassian.net/browse/YANG-7566

How to test

• [x] Create a discussion with manual comments approval, add a regular user as a moderator.
• [x] Open the discussion as the moderator, make sure there are no comments.
• [x] As a CM+ post a comment, make sure it is unpublished.
• [x] Open the discussion as the moderator, make sure the created comment is not displayed.
• [x] Clear cache, verify that the comment appeared.

Definition of done

Before merge

• [ ] Code/peer review is completed
• [ ] All commit messages are clear and clean. If applicable a rebase was performed
• [ ] All automated tests are green
• [ ] Functional/manual tests of the acceptance criteria are approved
• [ ] All acceptance criteria were met
• [ ] If applicable (I.E. new hook_updates) the update path from previous versions (major and minor versions) are tested
• [ ] This pull request has all required labels (team/type/priority)
• [ ] This pull request has a milestone
• [ ] This pull request has an assignee (if applicable)
• [ ] Any front end changes are tested on all major browsers
• [ ] New UI elements, or changes on UI elements are approved by the design team
• [ ] New features, or feature changes are approved by the product owner

After merge

• [ ] Code is tested on all branches that it has been cherry-picked
• [ ] Update hook number might need adjustment, make sure they have the correct order
• [ ] The Drupal.org ticket(s) are updated according to this pull request status