Implement oeo-ext logic & UI

[jh-RLI]

Summary of the discussion

The oeo-ext is a new member of the oef family. It allows users to extend the oeo with new values, but in a quick and informal way. For this reason, we have separated oeo and oeo-ext. The oeplatform provides the backend to store these new values and a user interface that can be used anywhere in the oeplatform when needed.

Type of change (CHANGELOG.md)

Features

• Add a new functionality (#)

Workflow checklist

Automation

Closes #1679 Closes #1712

PR-Assignee

• [x] 🐙 Follow the workflow in CONTRIBUTING.md
• [ ] 📝 Update the CHANGELOG.md
• [ ] 📙 Update the documentation on mkdocs

Reviewer

• [ ] 🐙 Follow the Reviewer Guidelines
• [ ] 🐙 Provided feedback and show sufficient appreciation for the work done