[ocis][time-boxed] Workflow Research

# Description

**usecases**
- trigger mail notifications like file changed/was uploaded/deleted ... https://github.com/owncloud/enterprise/issues/6715
- Clean up versions based on rules
- file retention - delete files based on rules / policies
- trigger approval process https://github.com/owncloud/enterprise/issues/5943

## User Stories

* > As owncloud we want todo some research for workflows to start this topic.

## Value

## Time Box

2 pd

## Acceptance Criteria

- look around what OSS projects are available
- Put together some "End User Usecases"
- Create a rough idea (ADR? confluence?) how to integrate workflows into ocis

## Definition of ready
[ ] everybody needs to understand the value written in the user story
[ ] acceptance criteria has to be defined
[ ] all dependencies of the user story need to be identified
[ ] feature should be seen from an end user perspective
[ ] user story has to be estimated
[ ] story points need to be less then 20

## Definition of done
- Functional requirements
[ ] functionality described in the user story works
[ ] acceptance criteria are fulfilled
- Quality
[ ] code review happened
[ ] CI is green
[ ] critical code received unit tests by the developer
[ ] automated tests passed (if automated tests are not available, this test needs to be created and passed
- Non-functional requirements
[ ] no sonar cloud issues