When you download a file directly from a Moodle form submit button,
the submit button disables when you click it, but you remain on that
page so we need to re-enable the button.
This commit causes it to re-enable once the file download finishes,
setting a temporary cookie to indicate this to the JavaScript code.
It also adds a method to disable the system on a given form by
setting data-double-submit-protection="off".
Forms subsystem has no own database table. The only personal data is the
user preference 'filemanager_recentviewmode' that stores the view mode
of the file picker element.
It was discussed whether handling of this preference should be added
here into core_form, or rather into core_repository subsystem. The final
decision was to consider the preference as owned by the core_form
because it is affecting the display of a form element, not the
repository backend (even though the strings describing it had been put
into core_repository strings).
While working on the filetypes element validation, I realized we did not
cover the case of selecting 'Any file type'. So the value '*' was
falsely reported as unknown file type.
These new methods will be used to render the tree of file types groups
and extensions in the browser widget.
Co-Authored-By: John Okely <john@moodle.com>
