[PLG] Approvals

[matmair]

### Closed Alpha
- [x] Dynamic approval requirements PLGAPR-1
- [x] Notification for all action PLGAPR-9
- [x] Reminders PLGAPR-14

### Public Beta
- [x] Gitlab-like pending state PLGAPR-8
- [x] Integration with *any* loaded model
- [ ] https://github.com/invenhost/plugins/issues/8

### Horizon 
- [ ] Dynamic rulesets PLGAPR-16
- [ ] More API options for ruleset manipulation
- [ ] Full change tracking
- [ ] Interactive notifications (MS Teams/Slack)

Summary

The approval plugin provides tools and integration for approvals/voting processes. The behaviour of approvals is controlled with pluggable rulesets that can be modified with plugins or

Meta

Current State: Closed Alpha
Alpha Available: 21/11/2023
Repo Public: Not planned
Code Public: Not planned
Project Tracking: https://mjmair.atlassian.net/jira/software/projects/PLGAPR/boards/2

[matmair]

Closed Alpha seats are full now

[matmair]

Pushing back repo public till upstream is done inventree/InvenTree#6017

[matmair]

Available now as beta! https://doc.invenhost.com/inventree_approval/main/