[PUI] Plugin settings UI (#8228)

* Visual tweaks for admin pages

* Provide admin js file via API

* Backend fixes

* Tweak error detail drawer

* Refactor plugin detail panel

- Split out into separate files
- Use <Accordion />
- Display custom configuration (if available)

* Refactoring

* Add custom configuration to sample UI plugin

* Bump API version

* Add separate API endpoint for admin integration details

* Refactor plugin drawer

* Null check

* Add playwright tests for custom admin integration

* Enable plugin panels in "settings" pages

* Fix for unit test

* Hide "Plugin Settings" for plugin without "settings" mixin

* Fixes for playwright tests

* Update playwright tests

* Improved error message

src/backend/InvenTree/plugin/samples/integration/user_interface_sample.py

@@ -21,6 +21,8 @@ class SampleUserInterfacePlugin(SettingsMixin, UserInterfaceMixin, InvenTreePlug
     DESCRIPTION = 'A sample plugin which demonstrates user interface integrations'
     VERSION = '1.1'
 
+    ADMIN_SOURCE = 'ui_settings.js'
+
     SETTINGS = {
         'ENABLE_PART_PANELS': {
             'name': _('Enable Part Panels'),
@@ -77,7 +79,7 @@ class SampleUserInterfacePlugin(SettingsMixin, UserInterfaceMixin, InvenTreePlug
         })
 
         # A broken panel which tries to load a non-existent JS file
-        if self.get_setting('ENABLE_BROKEN_PANElS'):
+        if instance_id is not None and self.get_setting('ENABLE_BROKEN_PANElS'):
             panels.append({
                 'name': 'broken_panel',
                 'label': 'Broken Panel',
@@ -90,7 +92,7 @@ class SampleUserInterfacePlugin(SettingsMixin, UserInterfaceMixin, InvenTreePlug
             panels.append({
                 'name': 'dynamic_panel',
                 'label': 'Dynamic Part Panel',
-                'source': '/static/plugin/sample_panel.js',
+                'source': self.plugin_static_file('sample_panel.js'),
                 'context': {
                     'version': INVENTREE_SW_VERSION,
                     'plugin_version': self.VERSION,
@@ -166,3 +168,7 @@ class SampleUserInterfacePlugin(SettingsMixin, UserInterfaceMixin, InvenTreePlug
             ]
 
         return []
+
+    def get_admin_context(self) -> dict:
+        """Return custom context data which can be rendered in the admin panel."""
+        return {'apple': 'banana', 'foo': 'bar', 'hello': 'world'}