closes https://github.com/TryGhost/Ghost/issues/10995
- when first loading the site preview, if private mode is enabled submit the login form in the background to get the cookie before loading the iframe
- refactors post-authentication preloading to ensure it occurs before post-authentication route hooks are called
- adds `showSuccess` attribute to `<GhTaskButton>` so that when set to `false` it can stay in the running state after "success" to avoid state change flashes whilst waiting for a transition
no issue
- adds an "Alt" button that is displayed in the caption input whilst an image card is selected, clicking it toggles between the rich-text caption input and a plain-text alt text input
no issue
- `app/helpers/gh-format-html` is duplicated in `lib/koenig-editor/addon/helpers/sanitize-html` and is not used anywhere else
- `app/helpers/gh-path` is not used anywhere - the API should be returning absolute URLs everywhere so path generation is no longer as necessary within templates
- `app/helpers/is-equal` replaced with `{{eq}}` from `ember-truth-helpers`
- `app/helpers/is-not` replaced with `{{not}}` from `ember-truth-helpers`
- `app/utils/isFinite` is not used anywhere
- `app/utils/titleize` is not used anywhere
no issue
- adjust drag handlers in the editor and gallery card to handle drag/drop of image cards as well as straight images
- adjust drag handlers in the gallery card to handle image inserts as well as re-orders
- add `onDragEnd` event/action to the Koenig drag-n-drop handler so that containers can perform cleanup if one of their draggables was successfully dropped into a different container
- change ghost element when dragging an image card to be an image rather than a card icon
- allow `createGhostElement` function passed in when registering a drag-n-drop container to fall back to the default behaviour by returning a falsy value
