Render python native docs alongside API docs

[niketagrawal]

This PR closes #144. Currently, the docstrings from python native modules are not being rendered on the API documentation website.

Summary of changes

• docs/source/conf.py: Modify the steps to build the docs on Read the Docs to use tudatpy dev conda package instead of multidoc. Point to the location where the binaries are stored, i.e., the location of the installation of tudatpy conda package on the machine.
• Include docstrings from the pure python modules in the below locations and render alongside api docs on the website:
  - https://github.com/tudat-team/tudatpy/tree/develop/tudatpy/numerical_simulation/environment_setup/gravity_field
  - https://github.com/tudat-team/tudatpy/tree/develop/tudatpy/numerical_simulation/environment_setup/ephemeris

Testing

The read the docs deployment of the changes in this PR can be viewed here: https://py.api.tudat.space/en/feature-144-include-python-native-docstrings/
Python native docstrings are rendered in https://py.api.tudat.space/en/feature-144-include-python-native-docstrings/ephemeris.html and https://py.api.tudat.space/en/feature-144-include-python-native-docstrings/gravity_field.html

To do

• Include the remaining python native files. See the list prepared earlier.
• Document steps to add/update API docs
• Cleanup multidoc related files form docs/ folder: To be done as a separate PR.

[DominicDirkx]

Thanks! Three questions/comments:

Include the remaining python native files. See the list prepared earlier.

which list where?

In the future, when adding a Python-native function to an existing tudatpy submodules and making sure the documentation shows up properly, what are all the steps that should be taken? Documentation for this can be a separate PR.

If the point:

Cleanup multidoc related files form docs/ folder

is purely aesthetic, let's put it in a different PR, then we can already test this out in our full pipeline.

[niketagrawal]

@DominicDirkx I was referring to this list:
python_files_tudat.xlsx

Should the docstrings in the python native modules marked as 'Keep' be rendered on the API docs website in the same way as the docstrings in horizons_wrapper.py and sbdb_wrapper.py are rendered in this PR?

[DominicDirkx]

Right, thanks! Yes, they should also be rendered along with the rest, but some files (starting with an underscore, I think) contain private functions that should not be part of the API.