Dark Energy Component Trait Class - #18447

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Let me know when you are ready and I will push changes to the changelog and such. I was puzzled by the failures last time around as all tests pass locally.

On a bus, sry. limited connection.
The RTD error is coming from

/home/docs/checkouts/readthedocs.org/user_builds/astropy/conda/18447/lib/python3.13/site-packages/astropy/cosmology/_src/flrw/base.py:docstring of astropy.cosmology._src.flrw.base.FLRW:1: WARNING: py:class reference target not found: astropy.cosmology._src.traits.darkenergy.DarkEnergyComponent [ref.class]
[3698](https://app.readthedocs.org/projects/astropy/builds/28907193/#279028093--3698)	/home/docs/checkouts/readthedocs.org/user_builds/astropy/checkouts/18447/docs/<rst_epilog>:2: WARNING: py:class reference target not found: astropy.cosmology._src.traits.darkenergy.DarkEnergyComponent [ref.class]

I think the DEComponent needs to be added to https://github.com/astropy/astropy/blob/main/astropy/cosmology/traits.py

I am on it. No rush please take your time. Will take me a bit to parse and get to the bottom of it.

So while I fix the docs I want to know if you want this to be publicly exposed or make it an internal reference only class. I just need to put that into base.py so docs can find it or skip accordingly.

Since this has an internal check for inv_efunc I think it can be public! Long term we'll want to move that check from inside the method to a subclassing or initialization check, but for now it's fine.

@nstarman Any suggestions on how to improve the code coverage for traits testing ?

@nstarman The test failure is not related to the code here. Thanks for looking it over. If you are up for it. I have the angular distances as the next one.