Update byo-firehose terraform module

[edwardsb]

Goal

Update byo-firehose module documentation and fix various issues encountered while deploying it into production

Context

byo-firehose module had some issues that were discovered while deploying into production environment. It also needed some documentation that describes what was actually going on under-the-hod.

[fleet-release]

Terraform module blooms,
Fixes weave, like clouds in glass,
Fleet thrives, understood.