Generate API documentation

[riley-harper]

We ought to generate some API documentation for LinkRun and all the related classes and functions that are part of hlink's API. These docs could be linked to from the current hlink.docs.ipums.org website, or they could be a subsection of that site.

I'm pretty sure that Sphinx is capable of generating this sort of documentation, so let's try that out sometime since we're already using Sphinx.

[riley-harper]

I looked into this, and with a combination of sphinx.ext.autodoc and sphinx.ext.napoleon, we should be able to generate nice documentation for the API. We may want to rework some of our docstrings to make them link to each other and look nice in Sphinx. One nice part about this process is that we can work directly in the sphinx-docs/ directory and have these pages be a part of the already-existing documentation.

[riley-harper]

Things to include in the documentation:

• LinkRun
• LinkTask
• LinkStep
• Table
• hlink.scripts.lib modules, like io and conf_validations
• hlink.configs.load_config
• SparkFactory and maybe SparkConnection