feat: add template option to display decorator

[ohrstrom]

Adds a template option to @display decorator.

The template option expects a Django template, which is rendered with the provided context.

class DemoAdmin(ModelAdmin):
    list_display = [
        "display_template",
    ]

    @display(
        description="Template",
        template="demo/admin/demo_template.html",
    )
    def display_template(self, obj):
        return {
            "name": obj.name,
            "count": obj.related.count(),
        }

<!-- demo/admin/demo_template.html -->
{{ name }} <sup>{{ count }}</sup>

This makes it easier to render arbitrary templates directly through the decorator, without needing to call render_to_string in the admin classes.

Would this be helpful?

[lukasvinclav]

Hey, first of all thanks for the idea. On one side, I understand why you need that but from my perspective I don't want push more logic into actions at the moment. Your implementation is fine but it still requires docs, tests and some examples in the demo project.