Add external coordinator

[KoalaSat]

What does this PR do?

Adds the option of including an external coordinator

Can be easily tested in local by removing an existing coordinator form frontend/static/federation.json and try to add it as external.

WARNING: This PR touches all important models so it requires good testing

Checklist before merging

• [x] Install pre-commit and initialize it: pip install pre-commit, then pre-commit install. Pre-commit installs git hooks that automatically check the codebase. If pre-commit fails when you commit your changes, please fix the problems it points out.