the html now contains a `data-prev-state` attribute which contains the
previous state, taken from the `operation` value in the form data (from
the submit button). This is used to seed the `currentState` of the
templateFolderForm. If not specified (or 'unknown', because the user
hit enter last time round), then set it to nothingSelectedButtons.
so that they better align with the front-end, where they'll be used in
data attributes. Also, making the kebab case is nice because it doesn't
give favouritism to either JS or python naming conventions
only remove the add template button if they have the folder service
permission (thus can see the add button at the bottom).
Also make some unnecessary functions into strings in the js, and
remove some commented out code
when cancelled, clears any data inputted into the sub-form action, and
then uses an icky hack to go back to the buttons, by changing the
state to "nothingSelectedButtons", and then pretending a checkbox was
clicked so it works out which actions to show and re-renders.
the action buttons have a value that matches up with the key for the
target form in the `this.states` object - we can just set the
currentState to that and call re-render and it all Just Works™.
detatch and reattach feel better than hide/unhide, mainly because it
means when the form is posted, any data that might linger in them
definitely won't be sent in the POST.
if action buttons are shown (either the nothing selected actions or the
stuff selected actions), when a checkbox is selected or deselected,
count how many checkboxes are selected. If it's zero, then show the
new template/folder buttons, if it's non-zero, then show the move
options.
Under the hood, we set the `currentState` variable, then the render fn
shows that element and hides all others.
have a bunch of separate elements within the sticky_template_forms div
that we hide or show based on button presses and such. This commit just
sets up the class - it doesn't actually deal with button presses or
checkboxes etc yet.
