Possibly move roxygen functionality into separate package from decoration functionality

[strazto]

Though these two components of {mandrake} have reasonably high cohesion, they have distinctly different applications:

• roxygen components:

  • Provides a common workflow within a package for documenting columns in a way that's consistent and cross referencable
  • Produces data that can be consumed by:
    • the decorators
    • packages inheriting columns from this package

• decoration components

  • consumes data produced by roxygen component
  • enriches visNetwork graph, and is tightly integrated with {drake}.

• Projects / packages that produce drake::drake_plans() will:

  • Directly use the decoration components, while
  • consuming data produced by packages that use the roxygen components.
    • the project may use the roxygen components, and dogfood its own colspecs, but not necessarily

• packages that provide data analysis/transformation/manipulation functions will:

  • Directly use the roxygen components
    • Potentially never use the decoration components

The shared components are the API for data consumption / production - the colspec format, and the caching / consumption mechanism thereof.

Given that decoration relies on roxygen, this mechanism should probably belong to the roxygen component.