Searching the docs for the phrases "add django model to wagtail admin" and "add model to wagtail admin" (without the quotes) did not even yield this crucial page as one of the results. The proposed wording puts the main idea of being able to show/edit ANY model via the Wagtail admin at the top of the document and includes wording to, hopefully, have this page appear at the top for anyone searching for how to implement this functionality.
* Split `helpers.py` into separate `url.py`, `permission.py` and `button.py`, dedicated to those separate concerns and update the docs accordingly
* Move `ThumbnailMixin` out to `mixins.py` and update documentation accordingly
* Ad #NOQA to import lines to hush pep errors
* Alphabetise helper import order
* - Delete `helpers/helpers.py`
- wagtal -> wagtail in docs
- Remove imports at the top of options.py and views.py that result in ImportError when those apps aren’t installed
- Alter ThumbnailMixin and InspectView to use the `wagtail.wagtailimages.shortcuts.get_rendition_or_not_found()` method to render images, which handles missing image source files gracefully, and reduces code duplication.
- Simplify `get_field_display_value()` by not limiting image and document rendering to ForeignKey fields. It should work consistently for property methods or other attributes too.
* `result_row_display` adds a `data-object_pk` attribute to each row, to make items easier to identify with JS
* Adds `get_extra_attrs_for_row()` method to `ModelAdmin`, to give developers a way of adding further attributes to the `<tr>` element
