Pull Request for Issue #27921

Summary of Changes

The associations button in the article edit form triggered the editAssocations task. That task invoked a save method in the model and then redirected to the association manager.
Unfortunately that save method bypassed everything done in the controller->save method. Resulting beside other potential issues in the issue above where the dateformat wasn't properly translated back.

This PR moves the code from the editAssociations method to the save method with a conditional on the active task.
in the controller, the "editAssociations" task is registered as a variant of the save method.

I have left the old "editAssociations" methods in the controller and model to keep B/C and added a deprecation note for 5.0.

Testing Instructions

• Test in the administrator backend using a language that doesn't use the regular english date format YYYY-MM-DD, for example german or russian.
• In a multilingual site, create an article assigned to a specific language.
• After saving the article, click on the "Associations" button in the edit form.
• It will redirect to the Associations Manager. In the new side-by-side form, check the created date of the article.

Expected result

Date is still there

Actual result

Date is empty

Documentation Changes Required

None