rename OPENAI_API_key env variable to be consistent with parseable vars.

[aldrinjenson]

• rename OPEN_AI_API_KEY env var
• remove unnecessarily passing in ai prompt body json to is_active route for llm

This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.