Tracking Issue: More Docs!

[alilleybrinker]

We need more documentation! This is a general purpose statement that would always be true, but in particular we've added a bunch of new concepts and functionality with the introduction of the plugin system, and it's not all documented clearly for users. This issue is intended to track documentation we ought to write.

• Explain targets structs and how they're passed to default queries

[ninaagrawal]

sdk/rust/src/mock.rs should have a comment at the top explaining purpose of the file. More comments throughout the file would be good

[ninaagrawal]

Giving more details about what configs are for plugins would be useful

[ninaagrawal]

For plugins/affiliation/src/until/org_types.rs, an annotation explaining what hosts are might be helpful. I think I saw some examples in the other files within the src directory but explaining what hosts are would still be good