refs https://github.com/TryGhost/Ghost/issues/7865
- updates all settings screens to use EC tasks and `gh-task-button` to get save-state save buttons
- removes now-unused `settings-save` mixin
- moves the order of button color CSS so that grey buttons can change to green/red after completing
- removes the heading from `apps-loading` template so that there's no odd flash when loading slack/amp screens directly
refs https://github.com/TryGhost/Ghost/issues/7515
- changes to `gh-task-button`:
- can take `buttonText` (default: "Save"), `runningText` ("Saving"), `successText` ("Saved"), and `failureText` ("Retry") params
- positional param for `buttonText`
- default button display can be overridden by passing in a block, in that scenario the component will yield a hash containing all states to be used in this fashion:
```
{{#gh-task-button task=myTask as |task|}}
{{if task.isIdle "Save me"}}
{{if task.isRunning "Saving"}}
{{if task.isSuccess "Thank you!"}}
{{if task.isFailure "Nooooooo!"}}
{{/gh-task-button}}
```
- update existing uses of `gh-task-button` to match new component signature
refs https://github.com/TryGhost/Ghost/issues/7255
- adds a `.appear-disabled` CSS class that doesn't prevent pointer events like `.disabled`
- updates `gh-task-button`:
- use `.appear-disabled` class instead of actually disabling button
- add check to guard against the button's assigned task being run multiple times whilst the spinner is running
This resolves the [user profile slug issue](https://github.com/TryGhost/Ghost/issues/7255) where clicking the Save button whilst the slug input has focus would only trigger the input's focus-out event due to it immediately disabling the button.
Update for synchronous feature service
Add client-side handling of server-side errors when adding subscribers
- display server-provided error message when we get a server error
- fix the ajax util's `getRequestErrorMessage` method so that it works correctly with Ember's `InvalidError` object instead of the previous request object that it was receiving (*TODO:* this really needs looking at properly so we aren't losing details and Ember Data can do it's stuff)
Styling updates
- proper icon for ascending/descending
- change hover colour to green for "Import CSV" button
Delete subscriber button with confirm modal
- display delete button when hovering over a subscriber row (WARN: really ugly button, styles definitely want looking at)
- show confirm modal when clicking the delete button
- delete subscriber, remove from table, and update total on confirm
- Modal button position tweaked, removed extraneous margin
- Fix user profile full name field and mobile profile-picture
- Added chevron to tag settings men, corrected chevron colour
- Fixed regression in delete-tag button caused by removing flexbox from buttons
- Fixed regression in button positioning on about-ghost page caused by removing flexbox from buttons
See #5652
- Lighter dropdown shadow
- Removed display:flex from .btn because safari can't handle it on <button> elements, where it will immediately set all text-alignment to "left" with no way to change. I haven't been able to find any regressions for this change so far. Can't remember why buttons were supposed to be flexbox anyway. Maybe for icon alignment within buttons, but I can't find any such examples within the app.
- Safari thinks that user-select: all; means a single click should SELECT ALL THE THINGS. Removed/replaced with user-select: text; which makes it behave like Chrome; click and drag to select.
- Increased hit area for "?" button
- Removed :active style for post-edit button on content management screen, adjusted position
- Increased contrast on tag description, tag count, and view blog links
See #5652
