[Epic] Approvals

[matmair]

This is a follow-up to #3501 which only required a simple flow. The following items should be relatively easy to implement - if the need for them arises. The code base was designed with them in mind.

### Rules
- [x] min number of approvers
- [x] max number of deniers
- [x] quorum
- [x] user attribute-based rules
- [x] time limits on cases

### Workflow optimisation
- [ ] dynamic template selector
- [ ] revocation/removal of approvals
- [ ] interactive slack/teams messages
- [ ] invite/request approval
- [ ] template import/export

### Advanced feature
- [x] rule templates
- [x] events/tracking of any changes (see stock tracking)
- [x] notifications for approvals

These features could be very interesting for Change Managment / ECO / ECR and maybe also for usage in plugins.

[SchrodingersGat]

@matmair thanks for taking the time to plan for these features and implement them here

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[matmair]

Those are mostly implemented in my plugin inventree_approval