Docs/missing flex config fields

[Flix6x]

Description

• Add missing field descriptions for aggregate-power
• Add missing field descriptions for state-of-charge
• Add missing field descriptions for commitments (although not fully specified, I think it is already useful to mention it exists)
• Purposely exclude relax-capacity-constraints, relax-site-capacity-constraints and relax-soc-constraints (we already document relax-constraints and the ability to set individual prices, and I don't want to overload users with information).
• Add a test to make sure all flex-config fields are present in scheduling.rst
• Added changelog item in documentation/changelog.rst

Look & Feel

How to test

pytest -k pytest -k test_all_metadata_fields_are_documented

Further Improvements

None

Related Items

Closes #2002

[read-the-docs-community]

Documentation build overview

📚 flexmeasures | 🛠️ Build #31673418 | 📁 Comparing dba851f against latest (b1a7022)

🔍 Preview build

Show files changed (3 files in total): 📝 3 modified | ➕ 0 added | ➖ 0 deleted

File	Status
changelog.html	📝 modified
api/v3_0.html	📝 modified
features/scheduling.html	📝 modified

[nhoening]

Approved, with one extra wish:

Under the commitments (not mentioned in the PR description?), it says "Support for this field in the UI is still under further development, but you can study the code to learn more.". Much better would be to link that to our new documentation page for commitments.