The autosave is reset on form submission, but if that form submission
happens at the same time as a page reload, the connection and/or server
is slow, then the connection may be aborted before the session is
removed.
This commit changes the autosave reset to use the fetch() API with a
keepalive flag.
Unfortunately we do not have a formal endpoint for this in Moodle JS so
this is a hackier approach than I would like. MDL-76463 has been opened
to investigate this.
This commit also fixes a situation where the autosave content is re-sent
when the user has typed in the editor and their next action is to click
on the submit button. This is now blocked for that editor instance.
Huong Nguyen