code cleanup tasks

[rahulbot]

This code has seen a few different authors at this point, and been forked and reassesed with some changing assumptions. I think we need to revisit this code to clean it up in a few ways:

• bring the coding norms in line with out other projects
• remove un-used or old features
• add more logging for traceability
• other things?

[pgulley]

Realizing that we compute aggregations for "significant" and "rare" terms as well as for "top"- my instinct is that we could excise them, as we never use them on the frontend

[rahulbot]

Yeah - we included those early to experiment with different results. The "top" seems most useful and stable, so perhaps we should just commit to those.

[pgulley]

Also, the api.py file is really bloated- I'm thinking it would be a worthwhile improvement in the developer experience if the the fastapi views and the actual elasticsearch logic were separated into two files

[pgulley]

Feeling like this is probably ready to close after the most recent round of polish I did