Implement new approach for plugin settings

- URL specifies plugin slug and setting key

InvenTree/common/tests.py

@@ -465,12 +465,35 @@ class NotificationUserSettingsApiTest(InvenTreeAPITestCase):
 class PluginSettingsApiTest(InvenTreeAPITestCase):
     """Tests for the plugin settings API"""
 
+    def test_plugin_list(self):
+        """List installed plugins via API"""
+        url = reverse('api-plugin-list')
+
+        response = self.get(url, expected_code=200)
+
     def test_api_list(self):
         """Test list URL"""
         url = reverse('api-plugin-setting-list')
 
         self.get(url, expected_code=200)
 
+    def test_invalid_plugin_slug(self):
+        """Test that an invalid plugin slug returns a 404"""
+        
+        url = reverse('api-plugin-setting-detail', kwargs={'plugin': 'doesnotexist', 'key': 'doesnotmatter'})
+
+        response = self.get(url, expected_code=404)
+
+        self.assertIn("Plugin 'doesnotexist' not installed", str(response.data))
+
+    def test_invalid_setting_key(self):
+        """Test that an invalid setting key returns a 404"""
+        ...
+
+    def test_uninitialized_setting(self):
+        """Test that requesting an uninitialized setting creates the setting"""
+        ...
+
 
 class WebhookMessageTests(TestCase):
     def setUp(self):