AI Engine Pro 2.6.8

* Add: Implemented the new OpenAI Assistants (Pro). It's beta, but it's there!
* Update: The former "Assistants" (which were tools in the Admin section) have been renamed into "Utilities".
* Update: Better control of who/what is using the REST API.

* Update: Cleaner way of handling errors in the chatbot.
* Update: Enhanced the way the files are uploaded, and follow the rules set by the Media Library.

* Update: Enhanced the Images Generator a lot, you can now add tasks to it, and let them run. The idea is to move this experience at some point to the Post Editor.
* Update: The URLs returned by DALL-E are now properly converted into Markdown (and therefore, HTML on the front-end).
* Update: Meow_MWAI_Query_Image is now using DALL-E 3 by default, and 1792x1024 as the resolution.
* Update: Better Discussions UI, displaying the images if they are still available.