Previously, the logic for copying an XBlock's OLX to the clipboard was directly in a POST view handler. This commit extracts it into a Python API function. In addition to following architectural guidelines [1], this change will help me develop the Content Libraries Relaunch, as I need a way to locally test library content reference via copy-paste while the UX for it is still being developed. [1] https://docs.openedx.org/projects/openedx-proposals/en/latest/best-practices/oep-0049-django-app-patterns.html