dhall: find target user for trying out entirely dhall-based customization pipeline

Created by: ggilmore

• implies architecture discussion is done and implemented
• implies with perf improvements have made it into a dhall release (link to dhall issue), or we have a workaround (docker?)
• implies either

1. We have implemented all the user's customization in their existing pipeline
2. Or we have a sufficient demo

• doesn't implies that the tool / docs is extremely polished, but the demo is clear enough that the major use cases are covered