[Refactor] Notification plugins (#9735)

* Refactor notification concept

- Notifications handled by plugins

* Cleanup

* Only send email if template provided in context

* Logic cleanup

* Fix log_error call

* Refactor error logging

- Ensure plugin slug is correctly attached
- Consistent format
- Logic fixes

* More robust plugin lookup

* Refactor calls to tringger_notification

* Tweak for build stock notification

* Low stock notification refactor

- Actually *use* the notification system
- Fix for email template

* Check stock only when build is issued

* Updated documentation

* Add PluginUserSetting class

- Allows plugins to define per-user settings

* Add API endpoints for PluginUserSetting model

* Placeholder for user-plugin-settings page

* Refactoring frontend code

* Placeholder panel

* Adds user interface for changing user-specific plugin settings

* Tweaks

* Remove old model

* Update documentation

* Playwright tests

* Update API version

* Fix unit test

* Fix removed arg

* Fixes for email notifications

- Track status of sending notifications
- Add helper "activate" method for plugin class
- Update unit tests

* Fix barcode tests

* More unit test fixes

* Test fixes

* Fix for settings models with extra fields

* Enhance unit test

* Remove old test file

* Check for null target_fnc

* Improve DB query efficiency

- Provide a flat list of active keys to plugin.is_active
- Prevents DB fetching (in certain circumstances)
- Add registry.active_plugins() method

* Bump query limit up for test

- In practice, this API endpoint is ~10 queries

* Handle potential errors

* Increase query limit for API test

* Increase query limit for some tests

* Bump API version

* Tweak unit test

* Tweak unit test

* Increased allowed queries

* fix user plugin settings

* Fix for unit test

* Update debug msg

* Tweak API

* Fix endpoint

* Remove "active plugin keys" code

* Restore previous behaviour

* Fix unit tests

* Tweak unit test

* Update src/backend/InvenTree/build/tasks.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/backend/InvenTree/plugin/base/integration/NotificationMixin.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Func updates

* Format

* Add notification settings

* Refactor plugin settings groups

* Fix func type

* Adjust message

* Additional unit tests

* Additional playwright tests

* Additional playwright test

---------

Co-authored-by: Matthias Mair <code@mjmair.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

docs/docs/plugins/builtin/index.md

@@ -19,8 +19,8 @@ The following builtin plugins are available in InvenTree:
 | [BOM Exporter](./bom_exporter.md) | Custom [exporter](../mixins/export.md) for BOM data | Yes |
 | [Currency Exchange](./currency_exchange.md) | Currency exchange rate plugin | Yes |
 | [DigiKey](./barcode_digikey.md) | DigiKey barcode support | No |
+| [Email Notification](./email_notification.md) | Email notification plugin | Yes |
 | [InvenTree Barcode](./inventree_barcode.md) | Internal barcode support | Yes |
-| [InvenTree Core Notifications](./notifications.md) | Core notification system | Yes |
 | [InvenTree Exporter](./inventree_exporter.md) | Custom [exporter](../mixins/export.md) for InvenTree data | Yes |
 | [Label Printer](./inventree_label.md) | Custom [label](../mixins/label.md) for InvenTree data | Yes |
 | [Label Machine](./inventree_label_machine.md) | Custom [label](../mixins/label.md) for InvenTree data | Yes |
@@ -28,8 +28,10 @@ The following builtin plugins are available in InvenTree:
 | [LCSC](./barcode_lcsc.md) | LCSC barcode support | No |
 | [Mouser](./barcode_mouser.md) | Mouser barcode support | No |
 | [Parameter Exporter](./part_parameter_exporter.md) | Custom [exporter](../mixins/export.md) for part parameter data | Yes |
-| [Part Notifications](./part_notifications.md) | Notifications for part changes | No |
+| [Part Update Notifications](./part_notifications.md) | Notifications for part changes | No |
+| [Slack Notification](./slack_notification.md) | Slack notification plugin | No |
 | [TME](./barcode_tme.md) | TME barcode support | No |
+| [UI Notification](./ui_notification.md) | UI notification plugin | Yes |
 
 ### Plugin Table