feat: Add 'unpublished' flag to configs

[kentquirk]

Which problem is this PR solving?

• We have some config options that we'd like to avoid publishing, because we don't know for sure we'll need them, but we want to give ourselves the ability to mess with them while tuning a configuration. By adding the ability to flag a config item as unpublished, it won't go in the main documentation and we can modify it later without breaking changes.

Short description of the changes

• Add unpublished flag to metadata struct
• Add it to a couple of fields
• Regenerate docs