splunk-hec always sends the message body and headers under the static json keys "body" and "headers" respectively.
Include an option that defaults to the current behavior of sending the body and the headers.
These new options `bodyOnly` and `headersOnly` should send either the body or the headers. If both are true then prefer headers. This also removed the need to create a map with static keys.
- Including the headers makes searching more tedious and our queries must always be prefixed with `body.`.
- Splunk charged based off of the amount of data you index. Indexing data you don't need can add up an unnecessary bill.